We have,

Introduce variable
such that 
The sum
is therefore 
So,
(sadia's age)
(father's age)
Hope this helps :)
Cos α = sin (90-α) so cos 19 = sin 90-19 = sin 71
Answer:
1) y = -2x - 1
2) y = -3/4 + 3
3) y = 4x + 9
4) y = - 5/3x - 2
Step-by-step explanation:
b = y - m*x
1) (-7,13) and slope: -2
b = 13 - (-2)*(-7)
b = 13 - 14
b = -1
2) (4,6) lope = -3/4
b = 6 - (-3/4)*(-4)
b = 6 - 3
b = 3
y = -3/4x + 3
3) (-5,-11) and (3,-7)
Slope: (1 - - 11)/(-2 - - 5) = 12/3
= 4
b = -11 - (4) (-5) = 9
b = 9
4) slope = (-7 - 8)/(3- - 6)
= -15/9 = - 5/3
b = 8 - (-5/3)*(-6)
b = 8 - 10
b = -2
Answer:
f(1) = √(4*1) = √4 = 2
The point (1, 2) is only on the third graph.