Video: Solving One-Step Addition Linear Equations Involving Decimals

Solve for 𝑥: 𝑥 + 4.8 = −8.9.

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Video Transcript

Solve for 𝑥: 𝑥 plus 4.8 equals negative 8.9.

This equation tells us that some value when we add 4.8 is equal to negative 8.9. When we see the word “solve” here, it means that we want to know which value for 𝑥 makes this statement true. If the equation has add 4.8, to solve it, we’ll need to do the inverse of adding 4.8. The inverse property says that any number added to its opposite will equal zero. But we also know, based on the subtraction property of equality, that if we subtract 4.8 from the left side of the equation, we must subtract 4.8 from the right side of the equation to make sure they stay equal. We now have on the left 𝑥 plus zero. We can just write that as 𝑥. And then, we have negative 8.9 minus 4.8, which equals negative 13.7. If we’ve calculated this correctly, we can plug in negative 13.7 in for 𝑥. And we’ll get a true statement.

We need to know is negative 13.7 plus 4.8 equal to negative 8.9. If we want to add 4.8 to negative 13.7, we subtract the two values first, which gives us 8.9 and then it takes the sign of the larger number. 13.7 was negative. So, the final answer will be negative. Negative 13.7 plus 4.8 does equal negative 8.9, which means the solution of 𝑥 is negative 13.7.

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