(1)
pq=2p+2q pq=5p-5q
5pq=10p+10q 2pq=10p-10q
7pq=20p q=20/7
3pq=20q p=20/3
(2)
xy=3x/8+y/4 xy=2x/7+3y/7
16xy=6x+4y 21xy=6x+9y
5xy=5y x=1
16y=6+4y 12y=6 y=1/2
(1)
pq=2p+2q pq=5p-5q
5pq=10p+10q 2pq=10p-10q
7pq=20p q=20/7
3pq=20q p=20/3
(2)
xy=3x/8+y/4 xy=2x/7+3y/7
16xy=6x+4y 21xy=6x+9y
5xy=5y x=1
16y=6+4y 12y=6 y=1/2