If DM=25, DG=r+2, GM=2r-13, what is the value of r?

Question

graph looks like this:

0----------------0----------------0

D G M

Answer 1

Segment DG and Segment GM are part of DM so they sum to equal DM

DG+GM=DM

Substitute the expressions above

r+2+2r-13=25

Combine like terms

3r-11=25

3r=36

r=12