Algebra

Here is the first one....you try the similar second one....

a-3 = sqrt (5a-9)        square both sides

a^2 - 6a + 9 = 5a-9    re-arrange

a^2 -11a +18 = 0

(a-9)(a-2) = 0      a = 9   or   2        test both answers.....you will find that only x = 9 works   (throw out '2')