Answer:
a) 140%
b) $62.50
Explanation:
a) Since the new cost is $59.99, this is x percent marked up. The original cost is $25 and that is 100% of the cost. The mark up will be a percent over 100%. To find this percentage set up a proportion with these values:

Solve for the original price by cross multiplying numerator with denominator.
x(25) = 59.99(100)
25x = 5999
x= 239.96
Subtract 100 to find the amount marked over 100%.
239.96-100 = 139.96
140% marked up
b) To find the sale price of jeans marked up 150%, use the same proportion except x this time will be the new price. The percent will be 250% or 100% + 150% = 250%

Solve for the original price by cross multiplying numerator with denominator.
x(100) = 25(250)
100x = 6250
x= 62.50