Question 1108392
David's current age = x
Martin's current age = x+3


The sum of their ages has us add up the two expressions (x and x+3) so we end up with (x)+(x+3) = x+x+3 = 2x+3


We're told that "the sum of their ages is 37", so set 2x+3 equal to 37 to get the answer 2x+3 = 37