question 1
area = 100 ( 50 x 2)
new area = 169 (increased by 69 percent )

169 = 84.2 x2

84.5 - 50 = 34.5
34.5 /50 = 69 %

this means arm length will also increase by same amount if other arm's length doesn't change .

question 2

area = a x b = ab
new area = 1.05a x 1.07b = 1.1235ab

new area - old area = 1.1235-1 = .1235 = 12.35 %