Answer: x = 20.
Step-by-step explanation:
x and (3x + 10) combine to form a right angle, shown in the diagram by the small square joining the perpendicular lines.
Right angles are 90 degrees, so you can add both angles to get 90:

Volume for rectangular prism is l x w x h
12cm x 6.5cm x 1.25cm = 97.5cm^3
I think the answer might be x=4/8
Point Slope Formula: y-y₁=m(x-x₁)
Linear Standard Form: Ax+By=C
Slope Intercept: y=mx+b