First find a common denominator between 7 and 4 which is 28, Multiply both equations by 28 eliminating the denominators so now you have theses two equations: 4(2x + 12) = 7(3x + 5) distribute these equations to get:
8x + 48 = 21x +35 now you want to get the x's on one side so 8-21 = -13 which as an equation so far would be -13x + 48 = 35 now do 35-48 = -13 so you can have 13x alone on one side. Your final equation now before you solve is