A snowflake falls 90 feet in 1 minute.
60 ÷ 4 = 15
6 x 15 = 90
This question isn't phrased correctly, but I will assume it's asking about common denominators with fractions.
9/11 1/22
18/22 1/22
18 school days.
The two equations are

and

the first equation can be solved for x to be

next you can substitute x in the second equation

Distribute 4 to everything in the parentheses

combine like terms:

subtract 28 from both sides of the equation

divide both sides by -1.5

plug this in to the original equation of x+y=7

subtract 4 from both sides.

Final Answer: they bought 3 adult tickets and 4 student tickets
Hope this helps!
So what you would do is put in the 4 where ever you see an x. so it would look like -3(4)+9y=-57 then you solve for y. and the answer is -5. Make sense?