Question 367423
Hey, 
For this one we need to split this problem into two equations:

a (adults) + c (children) = 590
3a + c = 1070
Then we substitute 590 - a for c in the second equation.
3a + 590 - a = 1070
2a + 590 = 1070
2a = 560
a = 280
Then we plug this into the first equation:
280 + c = 590
c = 310
I hope this helps!