Which equation would best help solve the following problem?

The height of a triangle is 5 m less than its base. The area of the triangle is 42 m^2. What is the length of the base?

A.) 42 = x(x - 5)
B.) 42 = 1/2(x)(x - 5)
C.) 42 = x^2 - 5
D.) 42 = 1/2(x^2 - 5)