Find the amount of simple interest that $400 would earn at 8% per year by the end of 3 1/2 years.

6n^2-7n-75=0 solve by quadratic formula

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.