Hi Bailey,
The area of the uniform distribution is always 1. Recall that the formula for area of any rectangle is:
A=lw, where l=length, w=width
So, here,
A=1
L=2, from length of x-axis
1=2w
w=1/2
Now, the area you were asked to calculate was 0.36 to 1.56. That, for our purposes, is a length, so we subtract:
1.56-0.36=1.2
Now, probability under a uniform curve is an area, so:
L=1.2
w=1/2, held constant
A=(1.2)(1/2)
A=0.60
I hope this helps.