Question

Explain which method you used for solving the system of equations in which x represents the number of bottles of water sold and y represents the number of sandwiches sold.

x + y = 390 and 2x + 4y = 1260

Answer 1

let use substitution to solve the equation
make x + y=390 in to linear form
y = 390-x
plug in y into the second equation
2x+4(390-x)=1260
2x + 1560 - 4x = 1260
-2x + 1560 = 1260
-2x = -300
x=150 bottles of water

now plug in x
150 + y = 390
y= 240 sandwiches

Answer 2

Sample Response: I used the linear combination method because both equations were in standard form. Before adding the equations together, I multiplied the first equation by –2 to eliminate x.

if you want to do your own include theses in your answer

Use the linear combination method.

Multiply the first equation by –2 to create opposite terms for x.

Multiply the first equation by –4 to create opposite terms for y.

Add the system of equations to eliminate a variable.