Tìm x

Bai 3. Tim x
a: (x + 2) + (x + 4) + (x+6) + (x + 8) = 36.
d.(x+1)+(x+2)+(x + 3) +.........(x + 98) +(x +99) = 6138
c. X x 1 + Xx 2 + Xx 3 + Xx4 + X x 5 = 300
e. X x 1 + Xx2+Xx 3 + Xx4+Xx 5+
g.X x 4+Xx 15 = 1919
a, 1+ 2+ 3+ 4+.
+ x = 210
8344 +156
.... X x 50
=
2550