Тема "пропорция". 1. x : 30 = 54 : 40 2. x + 2 / 2,4 = 8,5 / 6,8 3. 1 2/7 : 5 1/7 = 2/3 : x 4. 2x - 0,5/4,5 = 84/108

1. Х/30=54/40 Х=54*30/40=40.5 2. Х+2/2.4=8.5/6.8 Х+2=3. Х=5 3. 1 2/7: 5 1/7=2/3:Х 9/7:36/7=2/3:Х Х=0.375 4. 2х-0.5/4.5=84/108 2х-1/9=21/27 2х=3/27+27/27 2х=30/27 Х=30/27*1/2 Х=15/27 Х=5/9