Suppose that in one week, your company takes in $2,220 in sales at one of its cell phone stores. The price breakdown per phone is as follows:
Cell phone model A4: $35
Smartphone Z20: $50

Suppose that a total of 51 phones were sold.

this is the supposed problem with the method of solving in a graph

Question

Suppose that in one week, your company takes in $2,220 in sales at one of its cell phone stores. The price breakdown per phone is as follows:
Cell phone model A4: $35
Smartphone Z20: $50

Suppose that a total of 51 phones were sold.
  
this is the supposed problem with the method of solving in a graph

anonymous · Answer

you know that the revenue is 2220, which is the sum of all phones sold so:

2220 = 35*x + 50*y, with x='cell phones sold' and y='smartphones sold'

now; there are 51 phones sold in total, so x+y=51

this gives us the 2 equations relevant to this problem:
2220 = 35*x + 50*y
x+y=51

this can be solved in many ways, propably the easiest: 

x+y=51 => x=51-y

2220=35*x+50*y
2220=35*(51-y)+50*y
2220=35*51-35*y+50*y
2220=1785+15*y
15*y=2220-1785
15*y=435
y=435/15
y=29

x+y=51
x+29=51
x=51-29
x=22

anonymous · Answer

ok i got that part but i cant get how to graph it what do i insert for the graph to work