15 and 3 4ths times 5?

First, you would have to make the mixed number, 15 3/4, to an improper fraction, 63/4. You would multiply the whole number by the denominator, and add the product to the numerator, in this case 15*4+3 being 63. Then you would multiply by 5. 5 is the same as 5/1, and to multiply fractions, you have to multiply the numerators together to find the new numerator, and vice versa with the denominators. 63*5 is 315, and 4*1 is 4, therefore making the answer 315/4. Finally, you simplify to 78 3/4.