關於英文數學的問題

1
There are a total of 30 $50-cent coins and $2-coins in a money box, and the total value of the coins is $42. How many coins of each denomination are there in the money box??

2
The leagth of a rectangular flower bed is 0.25m greather than 3 times its width. The flower bed has a perimeter of 20.5m
(a) Find the length of the flower bed.
(b)Hence, find the area of the flower bed

Thanks

1)Let the number of $2-coins be n.

2n+(30-n)(0.5)=42

2n+15-0.5n=42

1.5n+15=42

1.5n=27

15n=270

n=18

∴There are 18 $2-coins and 30-18=12 $50-cents in the money box

2a)Let the width of the flower bed be n.
(3n+0.25+n)2=20.5
4n+0.25=10.25
4n=10
n=2.5

The length of the flower bed =3X2.5+0.25=7.75m

b) The area of the flower bed=2.5X7.75=19.375m