What is the formula for finding the area of a circle with radius r?

What number should be added to the expression x^2+3x+ in order to create a perfect square trinomial? 3/2 3 9/4 9

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

Acompany charges $0.10 for each letter engraved. bobby plans to spend no more than $5.00 on the engraving on a jewelry box. write and solve an inequality to find the maximum number of letters he can have engraved.