Tracey M. answered • 06/28/18

30 years as a tutor and volunteer in public schools

This is asking you to subtract (a - 2b - 3c + d) from (a - 2b + 3c)

So it's written in order like this:

(a - 2b + 3c) - (a - 2b - 3c +d)

You need to distribute the negative (subtraction sign) to each term in the second set of parentheses.

This will change the negatives to a positives and the positives to negatives

a - 2b + 3c - a + 2b + 3c - d

The a's cancel, the b's cancel

You're left with

3c + 3c - d

which equals

6c -d