Holt McDougal Larson Pre-Algebra Common Core Edition page 124 number 30

3.2r + 14.7 = 6.74

3.2r+14.7-14.7=6.74-14.7

3.2r=-7.96

3.2r/3.2=-7.96/3.2

r=-2.4875

Check:

3.2(-2.4875)+14.7=6.74

-7.96+14.7=6.74

6.74=6.74