Respuesta :
Answer:
The answer is A. 5 notebooks and 13 pencils
Step-by-step explanation:
1. Identify your x and y variables.
x - number of notebooks
y - number of pencils
2. Set up two equations to come up with a system of linear equations.
x + y = 18
2.3x + 1.25y = 27.75
3. In order to solve for one of the variables (either x or y), multiply the first equation with the additive inverse (when added together, the answer is zero; one number will be positive while the other number will be negative) of the coefficient of either x or y, so you can eliminate that variable. In this case, I choose the coefficient of y which is 1.25. So, the first equation will look like this:
-1.25(x + y) = 18
-1.25x - 1.25y = -22.50
4. Next, eliminate the y variable and solve for x.
-1.25x - 1.25y = -22.50
2.3 x + 1.25 y = 27.75
__________________
1.05 x = 5.25
1.05 1.05
x = 5 Joanna bought 5 notebooks.
5. Then, solve for y.
5 + y = 18
y = 18 - 5
y = 13 Joanna bought 13 pencils.
If you want to check your work, just plug in 5 and 13 into one of the two original equations. Simplify the equations, and you should get a true statement.
5 + 13 = 18
18 = 18
