Answer:
y = -2x + 100
where y and x are amount available on gift card and number of songs purchased.
Explanation:
Good day,
This is an interesting question from linear graph
what you need to do first is to find the gradient (slope)
The slope(m) = ∆y /∆x
= ∆amount available on gift card
----------------------------------------------
∆ number of songs purchased
=( 100 - 0/( 0 - 50) = 100/-50
= -2
pick any points on the line
(40,20)
where y1 = 20 , x1 = 40
now using the relationship
y = m(x - x1) + y1
y = -2(x - 40) +20
y = -2x +80+20
y = -2x +100
Do well to ask questions in you don't understand.
Gracias.