This is a lowest common multiple question.
to find the lowest common multiple, you need to find the prime factors of the two numbers:


Take out duplicates:

and multiply them together:

and that is your answer.
Easy peasy.
Answer:
(B)
Step-by-step explanation:

Plug in one of the two points for X and Y
(-3,1)

the students took math and physics = 55
Answer:
The ribbon cost per foot $0.6 per foot
Step-by-step explanation:
Total number of ribbon used = (5.75 + 11.75) = 17.50 feet
17.50 feet of ribbon cost = $10.50
1 foot of ribbon cost = x
Cross Multiply
17.50 × x = 1 foot × $10.50
x = 1 foot × 10.50/17.50
x = $0.6
The ribbon cost per foot $0.6 per foot