A relation is a function if it passes the vertical line test. That graph in a coordinate plane is just a sin wave that is spread out. If you run a perfectly vertical line through the graph at every place on the graph, the line you draw will only go through the graph at one place every time. That makes it a function. It's not a one-to-one function cuz it fails the horizontal line test, but it is a function!
Mammals: If the number of Mammal exhibits is 25 and there are 75 total exhibits, the Mammal exhibits are 1/3 of the total exhibits at this Zoo. The ratio for 1/3 is 1:3, which is 25:75 in most complex form. That's 33.3 as a percentage, or 33.3%.
Reptiles: If the number of Reptile exhibits is 15 and there are 75 total exhibits, the reptile exhibits are 1/5 of the total exhibits here. The ratio for 1/5 is 1:5, which is 15:75 fully written out. This as a percentage is 20%.
I'll message you the other half of the answers.