Answer:
1: x=y-3 linear equation : y=x+3
2:y=-2x-3 linear equation : y=-2x-3
3: -4y+6 =2 linear equation : y=2-6/-4 ⇒ y=1
4:2/3 x-1/3y=2 , linear equation : y=2x-6
-1/3 y=2-2/3 x
y=-6+2x
13: 5x+25=y² not linear
y = √5x+25
14 : 8+y=4x linear y=4x-8
15: 9xy-6x=7 not linear
16: 4y²+9=-4 ⇒ y²=-4/4 -9/4 ⇒y=√-1-2.25 ⇒y=√-3.25 not linear
17: 12x=7y-10y linear : y=12x/-3 ⇒ y=-4x
18:y=4x+x linear y=5x