Mental math is something that can be done i your head.
for example you can do 1+1 in your head and you dont need a calculator or paper to do it so i would be called mental math
Hope this helps
remember if you ever need anything and you dont want to waste points you can just post it on my pfp or message me the question
The ratio is called the Opposite leg or also known as Hypotenuse. Usually, in a right angle, the size of the one angle is 90 degrees while the other which is less than 90 degrees is called the hypotenuse. It is the opposite side of the angle measured 90 degrees
This may be wrong but I'm going to go with B. 1/7 x 9/10
Hope this helps! ( Probably didn't help in any way but I tried).
