x+2x+3x+4x+...+49x+50x-275=6100
1x+2x+3x+4x+...+49x+50x-275=6100
(1+2+3+4+...+49+50) . x-275=6100(co 50 so hang)
[(50+1) . 50 : 2 ] . x - 275 = 6100
1275 . x-275 = 6100
1275 . x = 6100 + 275
1275 . x = 6375
x = 6375 : 1275
x =5
Vay x=5
CACH LAM CO VE HOI SAI NHUNG X=5