We have to make 2 equations
A = Adults C= Children
So: A + C = 1300
15A + 10C = 17250
We can solve for A and C in 2 ways, SUBSTITUTION or ELIMINATION
I'll do substitution
SUBSTITUTION: Subtract A from both sides
A + C = 1300
-A -A
C = 1300 - A
Plug C is to the 2nd equation
15A + 10(1300 - A) = 17,250
15A + 13,000 - 10A = 17,250
5A + 13,000 = 17,250
- 13,000 -13,000
5A = 4250
---- ---------
5 5
A= 850
So, there are 850 adults, subtract 850 from 1,300 and there 450 children
Answer: 850 adults
450 children