Andrew M. answered • 01/30/18

Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors

s = Sam's age

m = Mary's age

k = Kate's age

s = 2m

m = k+5 , therefore, k = m-5

s+m+k = 31

In 3rd equation replace s with 2m; replace k with m-5; solve for m

2m + m + m-5 = 31

4m-5 = 31

Finish solving for m to get Mary's age.

Then use k = m-5 and s = 2m to find Kate and Sam's ages.