would go for B

Jims 4 hrs earnings= cost of jacket=Toms 5 hrs earnings
=> 4x=5y=C (x=jims hourly rate, y= toms hourly rate).......a

1) Tom makes 20% less per hour than Jim does
=>y=0.8x

putting it in..a above, we get 5y=4x
cant work out C from this. not sufficient

2) x + y = $43.75
=> putting x=5/4y (from a) , we can solve for y and hence the cost.
sufficient

Answer B

From the problem statement:

Jim requires 4x dollars (he earns x dollars per hour and needs to work 4 hours to earn enough money) to purchase the jacket.

Similarly Tom requires 5y dollars to pay for the same jacket

we can write that 4x = 5y

Statement A says that y = 80% of x => y = (4/5)x.
This is same as the equation we have already formed from the problem statement. Not sufficient to find the cost.

With Statement B, we have two equations and two variables, which we can solve for either x or y and find the cost of the jacket.

B alone is sufficient