let

s = the present age of Shelly

m = the present age of Michael

Shelly is 3 years older than michael:

s = m + 3

Four years ago the sum of their ages was 67:

s - 4 + m - 4 = 67

by solving the system of equations:

s = m + 3

s - 4 + m - 4 = 67

we find:

s = 39 years

m = 36 years

click here to see the step by step solution of the system of equations:

Shelly is 39 years old. Michael is 36 years old.