Hi there!
Let's solve this problem step by step!
If a coin is flipped 300 times and it landed 175 times in heads, we can find out that it landed on coins for 125 times, since 300 - 175 = 125.
Therefore the ratio heads to coins is
175 : 125
Now we can search for the simplest form of this ratio. We can divide both sides by 25 to find our answer (we do this because we must divide by the largest possible integer). When we divide both sides by 25, we find the following ratio
7 : 5
Hence, the answer is D. 7 : 5
~ Hope this helps you!