tolong bikin cara yaa,dua soal itu saya ga ngerti

No 21 jawabnya A
No 22 jawabnya A
Untuk caranya lihat digambar.

No.21
Misal :
Motor = x
Mobil = y
x + y = 30
2x + 4y = 90
Jawaban : A
Alasan => roda motor ada 2 , roda mobil ada 4
Jadi, 2x + 4y

No.22
5x + 2y = -3 | ×4 |
7x + 8y = 1 | ×1 |
------------------------
20x + 8y = -12
7x + 8y = 1
--------------------- -
13x = -13
x = -1

5x + 2y = -3
5 (-1) + 2y = -3
-5 + 2y = -3
2y = 2
y = 1

Maka,
x - y
= -1 - 1
= -2
Jawaban : A