Gosh, I've done this problem before. Let's start with 13. In this problem, we're basically just skip counting. For example, in the roses row, in the second bouquet, we know we have to add 4 more flowers, so we can document 8. Continue to skip count for both. For 15, we would have about 96 more movie posters remaining, making our ratio 96:x. So, 96:x = 120:100. Therefore, x would equal 80- as 96:80 equals 120:100. If she needs 80 and already had 100, she should sell 20 posters. Hope this helped.
For this case we must solve the following system of equations:

To solve we follow the steps below:
We multiply the second equation by -3:

Thus, we have the equivalent system:

We add the equations:

We look for the value of the variable "y":

Thus, the solution of the system is given by:

Answer:

Answer:
14-2a
Step-by-step explanation:
Since 15 and 21 are not included: we will have
=15-2a-1
=14-2a
Answer:
7 more students need to sign up.
Step-by-step explanation:
if you subtract the number of students needed by the number of students you have, you get 7 (30-23)