Hi! Love your book so far. I just started reviewing. I looked at number 10 in the first section on page 29 and I was wondering how would you pick the correct answer if you chose to substitute 8 for d? Because both answer choices a and d work. Would you just try all the answer choices and choose different variable values and try again or is there a different way to approach it?

Hi! Yes, when you plug in and see multiple answer choices that work, you have to try a new number and look at the choices again. Importantly, you only have to try the answers that worked the first time again. If B and C didn’t work the first time, you don’t need to try them again.