. При каком значении х справедливо равенство: а) x/21=3/7; b)31/72=93/x; c)-12/13=48/x; d)0,13/0,23=x/2,99; e)x/24=0,25;f)-0,8=27/x?.

Ответ:

a) x/21=3/7 -> x = 21×3/7 = 9

b) 31/72=93/x -> x = 72×93/31 = 72×3 = 216

c) -12/13=48/x -> x = 13×48/-12 = -13×4 = -52

d) 0.13/0.23= x/2.99 -> x = 0.13 × 2.99 / 0.23 = 1.69

e) x/24 = 0.25 = x = 24 × 0.25 = 6

f) -0.8 = 27/x = -33,75