The area of a triangle is given by the formula A=0.5bh, and the area of a rectangle is given by the formula A=lw. The area of the triangle plus the area of the rectangle equal the total area, which is 144. Therefore:
144=(0.5bh)+(lw)
Plug in 4 for b and 6 for l. w and h are both equal to x. The equation becomes:
144=(0.5*4x)+6x
*Combine like terms*
144=2x+6x
144=8x
*Divide both sides by 8*
18=x
Hope this helps!!