The length of GR is 20.
The ratio of BOY/GRL is 1/2. This gives us part of our proportion we will set up.
BO/GR = (x+3)/(3x-1); now our proportion is
(x+3)/(3x-1) = 1/2
Cross multiply:
2(x+3) = 1(3x-1)
Using the distributive property, we have
2*x + 2*3 = 1*3x - 1*1
2x + 6 = 3x - 1
Gathering all variables on one side, we subtract 2x:
2x + 6 - 2x = 3x - 1 - 2x
6 = x - 1
Adding 1 to both sides,
6+1 = x-1+1
7 = x
Since x=7, we substitute this into our expression for GR:
GR = 3x-1 = 3(7) - 1 = 21 - 1 = 20
