Question

7 repedeeeeee coroaaananaa

Answer 1

a, b direct proportionale cu 3 si 4 inseamna ca a/3 = b/4 si stim ca a + b = 21

a/4 = b/4 => a = 3b/4, inlocuim in a + b = 21 si obtinem 3b/4 + b = 21 ( inmultim cu 4 toata ecuatia si obtinem) 3b +4b = 84 => 7b = 84 => b = 12

si a + 12 = 21 => a = 21 - 12 => a = 9