5x+2y = 20
For every hardcover book (x) you will be charged 5$.
For every paperback book (y) you will be charged 2$.
The amount of both types of books you buy has to be under or equal to 20$
Count the total number of students who prefer fiction novels: In 9th grade there are 35, in 10th grade there are 52, so there are 87 students who prefer fictions. The proportion of 10th grade students out of these 87 students is 52/87=0.60 approximately.
Hello! Your answer is B, 10 minutes.
Say the x = minutes taken to do the job. You can set up an equation like this to solve this.

This is representative of the situation. The fractions each represent <u>how much each person does in a minute</u>, and when they're multiplied by x, that's <u>how much of the project they get done</u> based off of the minutes they work together on the job. Add the two together, and you get <u>how much of the project is finished in x amount of time</u>. Set it equal to 1, as you are looking for 100% completion.
Once you have this equation, find a common denominator, add, and solve.





Therefore, it will take them 10 minutes to do the job together.
Hope this helps!
Answer:
15 boys and 25 girls
Step-by-step explanation:
The sum of boys (b) and girls (g) is given as 40:
g + b = 40
The number of girls is 2 times the number of boys minus 5:
2b - 5 = g
First formula can be rewritten as g = 40 - b
Then you can substitute this for g in the second, and you get:
2b-5 = 40-b
Which simplifies to:
2b + b = 40 + 5
3b = 45
b = 15
g = 40-15 = 25
15 boys, 25 girls.