How is changing temperature similar to adding and removing floats and anchors on a submarine?

What is the value of  y  in the solution to the system of equations? x  +  y  =  12x  –  3y  =  –30a. –8b. –3c. 3d. 8

What is the solution to the equation 9^(x+1) =27

The base of a triangle exceeds the height by 7 centimeters. if the area is 400 square centimeters, find the length of the base and the height of the triangle.