Answer: a=24
Explanation:
Lets find the line's formula (equation of the line).
As known the general formula of any straight line (linear function) is
y=kx+b
Lets find the coefficient k= (Yb-Ya)/(Xb-Xa)=(9-7)/(-4-3)=-2/7
(Xb;Yb)- are the coordinates of point B
(Xa;Ya) are the coordinates of point A
Now lets find the coefficient b. For this purpose we gonna use the coordinates of any point A or B.
We will use A
7=-2/7*3+b
7=-6/7+b
b=7 6/7
So the line' s equation is y= -2/7*x+7 6/7
Now we gonna find the value of a usingcoordinates of point C.
Yc=1, Xc=a
1=-2/7*a+7 6/7
2/7*a= 7 6/7-1
2/7*a=6 6/7
(2/7)*a=48/7
a=48/7: (2/7)
a=24