about 49%
We can convert 63% directly to a decimal: 
63% = 0.63
Then, doing the calculation by hand or with a calculator, we find 
63% of 78 = 0.63 x 78 = 49.14 
 So the final answer is 
63% of 78=49.14 
You can round the decimal, if you're looking for a whole number, to about 49%.