We'll call the number of adults (x). Since there are 148 people total, the number of children will be 148 minus the number of adults, or (148 - x).
12 pounds for each adult = 12x
9 pounds for each child = 9 (148-x) = (1332 - 9x)
The total pounds for adults plus children is 1,410, so the equation would be:
12x + (1332 - 9x) = 1410
Combine like terms:
3x + 1332 = 1410
Get x term alone by subtracting 1332 from both sides:
3x = 78
Solve for x by dividing both sides by 3
x = 26 = number of adults