You can multiply them both as fractions or turn the fraction into a decimal and multiply it like that.
5 1/4 will have to turn into an improper fraction which means you have to get rid of the whole number so. To do so you have to multiply the whole number by the denominator which would be 5x4 which is 20 then add it to the numerator so I’d be 21.
Next turn the 3 into a fraction since it’s a whole number it’d be 3/1
Finally multiply straight across 21/4 x 3/1 which is 63/4 and luckily it’s already In it’s simplified form
