Answer:
12 starfish
Step-by-step explanation:
Create a system of equations where x is the number of starfish he has and y is the number of spiders he has:
x + y = 19
5x + 8y = 116
Solve by elimination by multiplying the top equation by -8:
-8x - 8y = -152
5x + 8y = 116
Add these together and solve for x:
-3x = -36
x = 12
So, he has 12 starfish.