4 (9+7x)+28=400
36+28x+28=400
28x=400-36-28
28x=336
x=336/28
х=12
25x+16x+13x=162
54x=162
x=162/54
х=3
4 (9+7x)+28=400
36+28x+28=400
28x=400-36-28
28x=336
x=336/28
х=12
25x+16x+13x=162
54x=162
x=162/54
х=3