For these type of problems, it is important to remember that fractions are basically numerators/denominators.
When multiplying fractions, you should multiply the numerators (7*4) and multiply the denominators (7*5).
Doing this will give you the answer of 28/35, which can be reduced to 4/5 by dividing each number by 7.
An easier way to do this is to know that any number divided by itself is 1 so 7/7 =1.
This problem then reduces to 1 * (4/5) which gives you the answer of 4/5.
Any number that is multiplied by one will result in the same number