1/2(7х + х) * 61 = 1220
4 х * 61 = 1220
244 х = 1220
х = 5
1/2(7x+x)*61=12200.5*8x*61-1220=0
4x*61-1220=0
244x-1220=0
x=1220/244
x=5
1/2(7х + х) * 61 = 1220
4 х * 61 = 1220
244 х = 1220
х = 5
1/2(7x+x)*61=1220
0.5*8x*61-1220=0
4x*61-1220=0
244x-1220=0
x=1220/244
x=5