Question

x*(1+2+3+.....+100)=60600

Answer 1

x* ( 1 + 2 + 3 + ... + 100 ) = 60600
x* [ 100 ( 100 + 1 ) : 2 ] = 60600
x * ( 100 * 101 : 2 ) = 60600
x * ( 50 * 101 ) = 60600
x * 5050 = 60600
x = 60600 : 5050
x = 12

Answer 2

$x. (\frac{101.100}{2})=60600 => x.5050=60600 => x= \frac{60600}{5050} = 12$