Studying for the act and i'm really bad at math, !

We are given the ratio of 1/2 inch: 18 miles

Multiply both sides of the ratio by 2. I'm doing this so that the "1/2" turns into "1"
So we go from this ratio
1/2 inch: 18 miles
to this ratio 
1 inch: 36 miles
which means that every inch on paper represents 36 miles in real life



The question is now: if two towns are 2.5 inches apart on paper, then how far are they in real life? (note: 2.5 is the decimal form of 2 and a half)

To find out, multiply both sides by 2.5
1 inch: 36 miles
2.5*(1 inch): 2.5*(36 miles)
2.5 inches: 90 miles



The two towns are 90 miles apart in real life

Sarah had gotten $75 from every lawn she mowed. she mowed x lawns. after multiplying 75 by x, she realized she owed her mother $20.