645 feet.
Explanation:
We know that are 3 feet in a yard, so let's set up a proportion to solve this
x215
3 feet n
-------- = -----------
1 yard 215 yards
x 215
We are solving for n. To get from 1 to 215, we multiply by 215. So to get from 3 to the answer, we must multiply by 215 as well. 3 x 215 = 645, therefore that is the answer.
Get one x+y=3 to y=x+3 and plug it into x-y=1 and you get x-(x+3)=1. Destitute the x and solve. Once you get what x equals plug it to to either equation for the value of x and solve for y
