A= √144/64 - √169/81
= √144/√64 - √169/√81
= √12²/8² - √13²/√9²
= 12/8 - 13/9
= 3/2 - 13/9
= 3x9/2x9 - 13x2/9x2
= 27 - 26/18
= 1/18
B= 3√36 -4√121/4√16 +3√9 -2√25 -3√49/3√64 +2√9
= 3√6² -4√11²/4√4² +3√3² -2√5² -3√7²/3√8² +2√3²
= 3x6 -4x11/4x4 +3x3 -2x5 -3x7/3x8 +2x3
= 18 -11/4 +9 -10 -7/8 +6
= -11/4 -7/8 +13
= -11x2/4x2 -7/8 +13x8/1x8
= -22 -7 +104/8
= 75/8
