Answer:
x = 6
Explanation:
x+3/15 = x+6/20
Should be written as: (x+3)/15 = (x+6)/20
(x+3)/15 = (x+6)/20
(15)*(x+3)/15 = (15)*(x+6)/20 [Multiply both sides by 15]
(x+3) = (x+6)*(15/20) [Combine and cancel units]
(x+3) = (x+6)*(3/4) [simplify]
(4/3)*(x+3) = (x+6)*(3/4)*(4/3) [Multiply both sides by (4/3)]
(4/3)x + 4 = x + 6 [Expand]
(1/3)x = 2 [Combine like terms]
x = 6 [Multiply both sides by 3]
CHECK
Does (x+3)/15 = (x+6)/20 when x = 6?
(x+3)/15 = (6+3)/15 = (9/15) or (3/5)
(x+6)/20 = (6+6)/20 = (12/20), or (3/5) YES
x = 6