Tolong no 83 dan no 84

semoga membantu yaa..

83) (a + 1)/4 - (a - 1)/3
= (3(a + 1) - 4(a - 1))/12
= (3a + 3 - 4a + 4)/12
= (7 - a)/12

84) (y - 2)/3 + (4 - y)/5
= (5(y - 2) + 3(4 - y))/15
= (5y - 10 + 12 - 3y)/15
= (2y + 2)/15
= 2(y + 1)/15