Six maths problems that I cant resolve Can somebode help me

Solution

20) Ax +By = C

point ( 12, 9) and line parallel to y =-7

So, the line for which we want to find the equation would be of the form : y =k

it passes through (12, 9) .So, y =9

comparing with std equation : A = 0 ; B =1 ; C = 9

21)

Ax +By = C

point ( -8 , -3) and line parallel to x =3

So, the line for which we want to find the equation would be of the form : x =k

it passes through (-8 , -3) .So, x = -8

comparing with std equation : A = 1 ; B =0 ; C = -8

22)

(1/24 , 1/6) and (1/28 , 1/7) Find slope:

slope = ( 1/7 - 1/6)/ ( 1/28 - 1/24)

=( -1/42) / (-4/672)

= 672/42*4

= 168/42

= 24/6

= 4