Here’s How to Crack It
First, pick a number for x. Pick something easy to work with, like 2. In your test booklet, write x = 2, so
you won’t forget. If x = 2, then 7x − 4 = 10, and x + 9 = 11. So, when x = 2, the expression in the problem
equals . Circle it! That is your target answer. When you find the answer choice that also gives you
when you plug in x = 2, you will know you have found an equivalent expression.
Start with the easier answer choices: (C) and (D). For (C), does 7 – = ? No! Eliminate it and move
on to (D): also does not equal your target answer, so it cannot be an equivalent expression.
Let’s try (B): When you put in 2 for x, you get 7 – . This is the number
that you are looking for. Unlike PITA, when you plug in your own numbers, you must check all four
answer choices, just in case more than one works. Go ahead and try the last answer just to make sure that
you’re right. Choice (A) does not give you your target answer, so you know that (B) is the one!
Get Real
Trying to imagine how
numbers behave in the
abstract is a waste of
time. So, if the problem
says that Tina is x years
old, why not plug in your
own age? That’s real
enough. You don’t have to
change your name to Tina.Here’s another example:
19.During a special sale at a furniture store, Erica bought a floor lamp at a 10% discount. She
paid a total of t dollars, which included the discounted price of the floor lamp and a 6%
sales tax on the discounted price. In terms of t, what was the original price of the floor
lamp?A)B) (0.9)(1.06)t