Question 79189
{{{ sqrt(63) - 2sqrt(28) + 5sqrt(7)}}}

{{{sqrt(7*9) - 2sqrt(7*4) + 5sqrt(7)}}}

{{{3sqrt(7) - 2(2)sqrt(7) + 5sqrt(7)}}}

{{{3sqrt(7) - 4 sqrt(7) + 5sqrt(7)}}}

same indexes and bases so add directly

{{{4sqrt(7)}}}