Because the first term on LHS has 'x' in the denominator and the second term in the LHS has '(x + 4)' in the denominator. So to get a common denominator, multiply and divide the first term with '(x + 4)' and the second term with 'x' as shown below
<span>Four gallons of paint cost $49.44. <span>Which equation can be used to find c, the cost per gallon? c=$49.44/4 c= $12.36 per gallon</span></span>