Three tenths of the sum of - 2 and - 28 written as numerical expression

Three tenths is the same as 3/10

the sum of - 2 and - 28 is - 30

3/10 of - 30 is the same as the products of the two

3 x - 30 / 10 = - 90/10 = - 9

Your answer is

3 (-2 + - 28) / 10 = - 9