tolong yang jago mateamtika nomer 2 bagian a ,b,c.

a. 
x = y
x + y = 6
subtitusikan x = y
x + y = 6
y + y = 6
2y = 6
y = 3
x = 3
HP : {(3,3)}

b.
y = 2x 
x + 3y = -21
subtitusi
x + 3y = -21
x + 3(2x) = -21
x + 6x = -21
7x = -21
x = -3

y = 2x
y = 2(-3)
y = -6
HP : {(-3,6)}

c.
x - 2y = 2
3y - 5x = -24

x - 2y = 2
x = 2y + 2
subtitusikan x ke 3y - 5x = -24
3y - 5x = -24
3y - 5(2y + 2) = -24
3y - 10y - 10 = -24
-7y - 10 = -24
-7y = -14
y = 2

x = 2y + 2
x = 2(2) + 2
x = 4 + 2
x = 6
HP : {(6,2)}