Question

(x+1)+(x+2)+.....(x+41)=40x +860

Answer 1

x+1+x+2+....+x+41=40x+860
41x+1+2+....41=40x+860
41x+ (41+1)×41÷2=40x+860
41x+42×41÷2=40x+860
41x+21×41=40x+860
41x-40x+861=860
x=860-861
x= -1

Answer 2

$(x+1)+(x+2)+.~.~.+(x+41) = 40x +860\\\\ x*41+(1+2+...+41)=40x+860\\\\ 41x-40x=860-(1+2+...+41)\\\\ x=860- \frac{42*(41+1)}{2}\\\\ x=860- \frac{41*42}{2}\\\\ x=860-861\\\\ \bold{x=-1}$