Evaluate 5a + 3b and (5 + a)(3+b) for a=2 and b=4 how is the order of steps diffrent from the two expressions

The first one = 10+12 = 22
second  = 7x7 = 49

the order of the steps are different by the pluses and minuses
the first one had a multiply to 5 and b multiply to 3 and add them together
the second one had a plus 5 and b plus 3 and those two multiplied .

Ya i could just need to know what type of math