Taking into account the definition of a system of linear equations, the price of each bag of popcorn is $8 and the price of each pretzel is $4.25.
A system of linear equations is a set of two or more equations of the first degree, in which two or more unknowns are related.
Solving a system of equations consists of finding the value of each unknown so that all the equations of the system are satisfied. That is, the values of the unknowns must be sought, with which when replacing, they must give the solution proposed in both equations.
In this case, a system of linear equations must be proposed taking into account that:
On one hand, Julia went into a movie theater and bought 2 bags of popcorn and 5 pretzels, costing a total of $37.25. This is expressed by 2x+5y= 37.25
Zoe went into the same movie theater and bough 8 bags of popcorn and 9 pretzels, costing a total of $102.25. This is expressed by 8x+9y=102.25
So, the system of equations to solve is:
[tex]\left \{ {{2x+5y=37.25} \atop {8x+9y=102.25}} \right.[/tex]
There are various methods to solve a system of equations, it is decided to solve by the substitution method, which consists of solving one of the two variables in one of the equations of the system and substituting its value in the other equation.
So, isolating the variable x from the first equation:
2x+5y= 37.25
2x= 37.25 - 5y
x= (37.25 - 5y)÷2
x= 18.625 - [tex]\frac{5}{2}[/tex]y
Replacing in the second equation:
8×(18.625 - [tex]\frac{5}{2}[/tex]y)+9y=102.25
Solving:
8×18.625 - 8×[tex]\frac{5}{2}[/tex]y+9y=102.25
149 - 20y + 9y=102.25
149 -11y= 102.25
-11y= 102.25-149
-11y= -46.75
y= (-46.75)÷ (-11)
y= 4.25
Finally, replacing in x= 18.625 - [tex]\frac{5}{2}[/tex]y and solving you get:
x= 18.625 - [tex]\frac{5}{2}[/tex]×4.25
x= 18.625 - 10.625
x=8
Remembering that x represents the price of each bag of popcorn and y represents the price of each pretzel, you get that the price of each bag of popcorn is $8 and the price of each pretzel is $4.25.
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