Question 971926
x=amount of money in saving's account; y=interest rate.

x* y=800  
x*(y+0.10)=2800; xy + 0.10x=2800

y=800/x

800 +0.10 x=2800
0.10x =2000
multiply by 10

x=$20000

800/20000=4%

14% on 20,000=$2800  Check

Rate of interest is 4% on savings and 14% on mini-mall.