My teacher gave me a worksheet and I don't understand this question. 25,75
GFC = Greatest Common Factor (ie: what is the biggest number you can divide both numbers by)
when the two numbers are 25 & 75 what is the biggest number that you can divide both by and get a whole number?
25 goes into 25 1 time. 25 goes into 75 3 times.
so the GCF = 25