tentukan nilai a. usahakan menggunakan caraa! tlong

90 = 3a + 2a
90 = 5a
a = 90 ÷ 5
a = 18

180 = 90 + 2a + 3a
180 = 90 + 5a
180 - 90 = 5a
90 = 5a
90 ÷ 5 = a
18 = a

^^