Isaac downloaded 7 ringtones. each polyphonic ringtone costs $3.25, and each standard ringtone costs $1.50. if he spends a total of $21 on ringtones, find the number of polyphonic and standard ringtones he downloaded.

 and

Step-by-step explanation:

Let

x -----> the number of polyphonic ringtones

y ----> the number of standard ringtones

we know that

-----> equation A

-----> equation B

Solve the system of equations by substitution

Substitute equation A in equation B and solve for y

Find the value of x

the slope of the first function is -3. (3/1)

the slope of the second function is 1. (13-10/6-3).

since |-3| is greater than |1|, the function with the steepest slope is the first.

you first to choose the points and then move from then as the slope you have