Take the 30 and divide it by 100 and you get the percent. Ex. 30/100 = .3
Then multiply 64 by the percent. 64 x .3 = 19.20
To find what percentage 30 is of 64, divide 30 by 64 to get approximately 0.46875, then multiply by 100 to convert to a percent, which gives you about 46.88%.
;