Equations with Addition and Subtraction

Mr. Squeaks has time traveled to England and is spending a lot of time in this lab doing experiments. "Mr. Squeaks! What have you done?!" "Now I am Doctor Squeaks, if you want Mr. Squeaks back, you'll have to follow these directions!" In order for Imani to change Doctor Squeaks back to Mr. Squeaks, they need to follow the directions and solve... Equations with Addition and Subtraction. An equation tells us that the expression on either side of the equal sign (...) is EQUAL to the other. Equations can be used to solve word problems. First, Read the word problem. As you read, think; 'what do I need to find?'... and highlight the question you need to solve! For example... in order to reverse the experiment, Imani needs seventy-eight ingredients altogether. The directions say they need twenty-four jars of mist and fourteen rose petals. The rest of the ingredients they need are crystals. How many crystals does Imani need? Here we highlight “How many crystals does Imani need?”... because it asks us to find how many crystals are needed to reverse the experiment. Now, reread and think; 'What is the important information?' While rereading, highlight keywords, numbers, or units of measurement, that will help answer the question. In the first sentence... highlight seventy-eight ingredients altogether, (...) because this tells us the total number of ingredients they need. In the next sentence, highlight twenty-four jars of mist and fourteen rose petals (...) because this tells us how much of each ingredient they need. Also highlight, the rest of the ingredients they need are crystals (...) because that is the unknown value, or what we're trying to figure out. Then, identify the operation. We can't identify the operation just yet, so we move on to the next step. The next step is to write the equation using a VARIABLE to represent the unknown value. A variable is a letter used to represent the value that we're solving for. Our equation is: twenty-four jars of mist plus fourteen rose petals plus equals seventy-eight... because if we add all the ingredients together, the total number they need is seventy-eight. We use the letter as the variable to represent the number of crystals. Last, solve the equation... but how do we solve for the number of crystals or ? (...) First, we add twenty four jars of mist and fourteen rose petals. Twenty-four plus fourteen is thirty-eight. But we still don't know how many crystals we need! How do we calculate the number of crystals? (...) Subtract thirty-eight from the number of ingredients in total, which is seventy-eight. What is seventy-eight minus thirty-eight? (...) Forty, write the answer using the variable equals forty. Imani needs forty crystals to reverse the experiment! Remember (...) an equation tells us that the expression on either side of the equal sign (...) is EQUAL to the other. Equations can be used to solve word problems. When writing the equation we use a variable to represent the unknown value. Always include the variable in your answer using an equal sign. "Mr. Squeaks! You're back, no more Dr. Squeaks!" "What are you talking about Imani? Let's get you back home..."