First reduce, (if possible), then multiply the numerators into one numerator, and multiply the denominators into one denominator.
4 x 10 = 40
5 12 60
To divide fractions...
multiply the first fraction by the reciprocal of the second.
(2/3) / (4/5) = (2/3) * (5/4)
To add or subtract fractions...
Find the common denominator, then add or subtract the numerators as normal.
A shortcut would be to use the "Bowtie" method - Multiply the first numerator by the second denominator, and vice versa to find the new numerators, and multiply the denominators to find that new value. Then, add or subtract as normal.