mohon bantu ya dengan caranya.....

x1 = x2 - 2
x2
x3 = x1 + 4 = (x2 - 2) + 4 = x2 + 2

x1 + x2 + x3 = 21
(x2 - 2) + x2 + (x2 + 2) = 21
3x2 = 21
x2 = 7
x1 = 5
x3 = 9

#semoga membantu