The pieces are already the same size, so add the numerators and keep the denominator.
two sevenths + three sevenths = five sevenths
2 sevenths and 3 sevenths make 5 sevenths.
five eighths + seven eighths = twelve eighths
5 + 7 = 12, so the sum is 12 eighths. That is more than 1 whole, so the numerator is larger than the denominator. Enter it as a fraction.