.
You can start from these equations
A + C = 14 (1) (counting people)
9A + 5C = 110 (2) (counting money)
where C and A are the numbers of children and adults, respectively.
From equation (1), express C = 14-A and substitute it into equation (2)
9A + 5*(14-A) = 110. (3)
Next, simplify and solve
9A + 5*14 - 5A = 110
4A = 110 - 70 = 40
A = 40/4 = 10.
ANSWER. 10 adults and 14-10 = 4 children.
You also can start from equation (3) directly, if you want to setup the problem in 1 (one) single equation.
-------------
It is a standard tickets problem.
There are different methods of solving such problems.
In this site, there are the lessons
- Using systems of equations to solve problems on tickets
- Three methods for solving standard (typical) problems on tickets
explaining and showing all basic methods of solving such problems.
From this lesson, learn on how to solve such problems once and for all.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lesson is the part of this online textbook under the topic "Systems of two linear equations in two unknowns".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.