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!
Square b area = 144 ÷ 2
area = 72 in squared
area in feet = 6 ft squared