4, -4/8 = x/-10 = -7/y = z/-24
=> 8.x = -4 . -10
=> 8.x = 40
=> x = 5
Thay x = 5 ta có: 5y = -7.(-10) 
=> 5y = 70    => y = 14
thay y =14 ta có: 14z = -7.-24
=> 14z = 168   => z = 12
5,  a, ta có -35/7 = -5
mà -35/7 < x <= -1   suy ra x ∈ { -1; -2; -3; -4}
b, ta có: -18/6 = -3  ;  144/72 = 2
Mà -18/6 <= x <= 144/72   suy ra x ∈ { -3; -2; -1; 0; 1; 2}
6, 12/-24 = -1/2
-39/75 = -13/25
132/-264 = -1/2
7, 11.4 - 11/2-13 = 11.(4-1) / -11 = 11.3/-11 = -3
b, 8.5 - 8.2 / 16 = 8.(5-2) / 16 = 24/16 = 3/2
c, 153.24 - 153.11 / 7-160  = 153.(24 - 11) / -153 = -13
8, 3.5 / 8.24 = 5/64
b, 2.14 / 7.8 =1/2
c, 3.7.11 / 22.9 = 7/6