The value of the expression
is 
<h3>How to evaluate the sum?</h3>
The attachment represents the proper format of the question
The summation expression is given as:

Expand the radicands

Evaluate the square roots

Add the like terms

Hence, the value of the expression
is 
Read more about expressions at:
brainly.com/question/723406
#SPJ1
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!
Idk what are your questions?
Answer: what do you have to do ??