1) sin130>0, cos100<0, cos20>0, cos90=0.
Правильно: 3).
X+2x-5=40
3x-5=40
3x=40+5
3x=45
x= 45\3
x=15
15x + 48x = 1512
63x = 1512
x = 1512 : 63
x = 24
15 x 24 + 48 х 24 =1512-проверка
15 х 24 =360
48 х 24 =1152
360 + 1152 =1512
1512 = 1512
A + b = 29/6 (7/6 + b) + b = 29/6
a - b = 7/6 2b = 29/6 - 7/6
a = 7/6 + b b =11/6 1і 5/6
a = 7/6 + 11/6 = 3