(х-4)*6=138

6 * x - 24 = 138

6 * x = 138 + 24

6 * x = 162

x = 162 / 6

х= 27

(107-х):2=51

107 - x = 102

x = 107 - 102

х= 5

64:х+13=29

64 + 13 * x = 29 * x

16 * x = 64

x = 4