The local home improvement store wants to increase their inventory. last year 40 lawn mowers cost them $4,776. at the same cost, how much would 120 lawn mowers cost them this year?

To solve this, set up a proportion where X is the amount that 120 lawn mowers would cost. It would look like .

Then cross-multiply to get 40x = 120(4776) or 40x = 573120. Now divide each side by 40 to isolate the variable. 

X = 14328. 

120 lawn mowers would cost $14,328.