Question

X+3x+5x+....++37x+39x=2000

Answer 1

$x + 3x + 5x + ... + 37x + 39x = 2000$

$x(1 + 3 + 5 + ... + 37 + 39) = 2000$

$1 + 3 + 5 + ... + 2n - 1 = {n}^{2}$

$2n - 1 = 39$

$2n = 39 + 1$

$2n = 40 \: | \div 2$

$n = 20$

${n}^{2} = {20}^{2} = 400$

$x \times 400 = 2000 \: | \div 400$

$x = 5$