數學題唔識(急用)

a) let y be the marked prices of the bag.

y=a(1+30*)
y=1.3a

so the marked prices of the bag is $1.3a.

the marked price of the swim suit= $(1.3a-50)

b) 1.3a+1.3a-50=470
2.6a=520
a=200

therefore the cost price of the bag is $200.

let $z be the cost price of the swim suit.
1.3a-50=z(1+40%)
1.3(200)-50=1.4z
z=150

therefore the cost price of the swim suit is $150

Let a be the cost of bag
let b be the cost of swim

1.3a-50=1.4b
b=(1.3a-50)/1.4

b) 1.3a+1.4b=470
1.3a+1.3a-50=470
a=200
b=150