If DM = 60, DG = 4r and GM = r+5, what is the value of r?

Question

solve for r 

Answer 1

D----------------G--------M

mDM=mDG+mGM

60=4r+(r+5)

60=4r+r+5

60=5r+5

60-5=5r

55=5r

r=55/5

r=11

check: 4r=44, r+5=16, 44+16=60