This is gonna be a long answer but it will help...
Answer:
Cost price of the burger = $4.15
Step-by-step explanation:
Given data:
3 burgers were ordered
3 medium fries were ordered
Total order cost 17.55
Let the price of the burger be X
Let the price of the medium fries be Y
Equation for the total sale will be 3X + 3Y = 17.55 (equation 1)
from this statement 'The price of a burger is .75 more than two times the price of medium fries.'
X - 2Y = 0.75 (equation 2)
There are now two equations and two unknowns, a simultaneous equation is solved to find the cost of the burger.
Many methods can be used to solve these equations but in this case substitution will be used
From equation 2
X = 0.75 + 2Y (equation 3)
Substituting equation 3 into equation 1
3(0.75 + 2Y) + 3Y = 17.55
2.25 + 6Y + 3Y = 17.55
6Y + 3Y = 17.55-2.25
9Y = 15.3
Y = 1.7
Substituting Y into equation 3
X = 0.75 + 2Y
X = 0.75 + 2(1.7)
X = 0.75 + 3.4
X = 4.15
Therefore the cost price of the burger is $4.15
