Provider B electricity would be cheaper for Catherine.
If Stephanie pays the same price for electricity whether she uses provider A or provider B, then she uses 300 kWh of electricity per month.
Which provider would be cheaper for Catherine?
Provider A:
y = x/12 + 15
Provider B:
y = x/20 + 25
1.
If Catherine uses 360 kWh per month
Provider A:
y = x/12 + 15
= 360/12 + 15
= 30 + 15
y = 45
Provider B:
y = x/20 + 25
= 360/20 + 25
= 18 + 25
= 43
Provider B electricity would be cheaper for Catherine
2.
Equate the two providers
x/12 + 15 = x/20 + 25
combine like terms
x/12 - x/20 = 20 - 15
5x-3x/60 = 10
2/60x = 10
x = 10 ÷ 2/60
x = 10 × 60/2
= 10 × 30
= 300 kWh
Therefore, Stephanie uses 300 kWh of electricity per month