If C + D = 9 and C and D are positive integers, which of the following is a possible value for 5C + ...

If C + D = 9 and C and D are positive integers, which of the following is a possible value for 5C + 8D?

Quiz

Answer/Solution

90

Steps/Work

c + d = 11
5c + 8d = 5c + 5d + 3d = 5(c+d) + 3d = 45 + 3d=D=15
D=15
c+d=9=C+15=9=C=9-15=-6
C=-6
5C + 8D=5(-6)+8(15)=-30+120=90
Hence, D is the right answer.