Answer:
1. The cost increases $0.30 each time 1 goldfish is
added.
Let's say the first number is "a"
the next consecutive can just be "a+1" and the next, you guessed it, "a+2"
the two smaller ones are a and a+1, the larger one is a+2
now, the product of "a" and "a+1" equals 5 times "a+2" but less by 5
thus a(a + 1) = 5(a + 2) - 5 <----- solve for "a"
Answer: it’s the first one
Step-by-step explanation: