Jawab yang 21 sama 22 dong... terima kasih

22.
2x + 7y = 25
x + 4y = 14

eliminasi kedua persamaan diatas
2x + 8y = 28
2x + 7y = 25
_________-
y = 3

cari nilai x dgn subtitusi
x + 4y = 14
x + 4(3) = 14
x + 12 = 14
x = 14-12
x = 2

pertanyaannya
x + 3y
=2 + 3(3)
=2+9
=11

21.
m = (y2 - y1)/ (x2 - x1)
7 = (5p - 3) /(3-p)
5p - 3 = 7(3-p)
5p - 3 = 21 - 7p
5p + 7p = 21 + 3
12p = 24
p = 24/12
p = 2