1) 253 -х +459=138
-х=-253-459+138
-х= -574
х= 574
2) 502-217+х=421
х=-502+217+421
х=136
3) 871 - х-157=385
-х=-871+157+385
-х=-329
Так включи калькулятор и решай)
54 + 5 = 59 48 + 3 = 40 + (8 + 3) = 40 + 11 = 51
63 + 4 = 67 37 + 7 = 30 + (7 + 7) = 30 + 14 = 44
91 + 8 = 99 28 + 6 = 20 + (8 + 6) = 20 + 14 = 34
45 + 4 = 49 36 + 9 = 30 + (6 + 9) = 30 + 15 = 45