Question Video: Evaluating Algebraic Expressions Using Proportion Equations Mathematics • 7th Grade

Video Transcript

If 𝑥 over 𝑦 equals eight over 21, determine the value of 𝑥 plus 𝑦 over 𝑥 minus 𝑦.

So, what we’re gonna say is that 𝑥 is equal to eight and 𝑦 is equal to 21. So therefore, if we’ve got 𝑥 plus 𝑦 over 𝑥 minus 𝑦, what we can do is substitute in these values. Which is gonna give us eight plus 21 over eight minus 21. Well, eight add 21 is 29. And eight minus 21 is negative 13. So therefore, we can say that if 𝑥 over 𝑦 equals eight over 21, then the value of 𝑥 plus 𝑦 over 𝑥 minus 𝑦 is gonna be equal to negative 29 over 13.