Shelly is 3 years older than Michelle. Four years ago, the sum of their ages was 67. Find the age of each person now

S = 3+M

4 (S + M) = 67

4 (3+M + M) = 67

4 (3+2M) = 67

12 + 8M = 67

8M = 55

M = 6 years 10 months 14 days @ 6.875 years

S = 3 + 6.875

S = 9 years 10 months 14 days

You'd set the equation up as such: 3+M + M = 71 (I got 71 because the age increased by 4 years which means it increased 4 more than 67). You'd combine like terms - 2M + 3 = 71, subtract both sides by 3 thus equally 2M=68, then divide both sides by 2, equally M = 34. Plug Michelle's age in at 34 and then Shelly is 3 years older at 37.