Первое число x, второе y.
(x+y)/2=30;
x-y=9.8;
x=y+9.8;
(9.8+y+y)/2=30;
9.8+2y=60;
2y=60-9.8;
2y=50.2;
y=50.2/2;
y=25.1;
x=25.1+9.8;
x=34.9;
1) 134 + Х = 426 + 583
134 + Х = 1009
Х = 1009 - 134
Х = 875
2) 208 +Х - 416 = 137
208 +Х = 137 + 416
208 + Х = 553
Х= 553 - 208
Х = 345
1) 21+ 29 = 50
2) 160 - 90+ 70
3) 328-258=71
4) 250-50 = 200
5) 33+ 367 = 400
6) 150+40 = 190
7) 98 + 102 = 200
8) 900- 480 = 420
17(5х-16)=238
85х-272=238
85х=238-272
85х=-34
х=-0,4