a) y/3 + y/4 + 15 = y | * 12
(12y)/3 + (12y)/4 + 15*12 = 12y
4y + 3y + 15*12 = 12y
15*12 = 5y | : 5
3*12 = y
36 = y
Probe:
36/3 + 36/4 + 15 = 12 + 9 + 15 = 36 stimmt.
b) 2x-5/2 = 4x-9/5 | Unklar, was alles über dem Bruchstrich sein soll.
c) (5y)/8 = (2y)/5 + 3 | * 40
(200y)/8 = (80y)/5 + 120
25y = 16y + 120
9y = 120 |:9
y = 120/9 = 40/3 = 13 + 1/3 = 13 ^1/_(3)