I don't know what you mean by benchmark but this is adding fractions. when you add fractions you must have the same denominator. 10 and 5 are not the same so you need to find the same denominators conveniently 2/5 is equivalent to 4/10 (by multiplying the fraction by 2) then you add the numerator straight across keeping the same denominator. that would be 5/10. Simplify to the is 1/2