Let u be the units digit. Then the tens digit is u+3, while the hundreds digit is 2*(u+3). Notice that 2*(u+3) must be less or equal to 8, so 2(u+3) <= 8, so u+3 <= 8/2 = 4, which gives 0 <= u <= 1 Thus the formula for the value of the 3-digit number is 100*2*(u+3) + 10*(u+3) + u = 200(u+3) + 10*(u+3) + u, where " u " is EITHER 0 or 1. If u = 0, then the 3-digit number is 630; if u = 1, then the 3-digit number is 841.