108. Пропорции.
a) 4x/5 = 7/8
4x = 7*5/8 = 35/8
x = 35/(8*4) = 35/32 = 1 3/32
b) 8/3 = 19/(3 - 11x)
8(3 - 11x) = 3*19 = 57
3 - 11x = 57/8
11x = 3 - 57/8 = (24 - 57)/8 = -33/8
x = -3/8
c) (2 - 3x)/(11 + 2x) = 7/2
2(2 - 3x) = 7(11 + 2x)
4 - 6x = 77 + 14x
-6x - 14x = 77 - 4
-20x = 73
x = -73/20 = -3 13/20
109. Решается точно также.
a) 11/(16x) = 2/5
16x*2 = 11*5
32x = 55
x = 55/32 = 1 23/32
b) 18/(1 + 5x) = 4/3
4(1 + 5x) = 18*3 = 54
1 + 5x = 54/4 = 27/2
5x = 27/2 - 1 = 25/2
x = 5/2 = 2,5
c) (12x + 1)/(4 - 3x) = 50/(-4)
(12x + 1)(-4) = -50(3x - 4)
-48x - 4 = -150x + 200
150x - 48x = 200 + 4
102x = 204
x = 2