#35. Mahmud invested $6000 in two accounts, some of it at 4% simple interest, the rest of it in an account earning 2% simple interest. How much did he invest in each account if he earned $190 in interest after 1 year?

Start by "naming" things. Let "x" be the amount of money invested at 4% interest. The interest on that is .04x. Let "y" be the amount invested at 2% interest. The interest on that is .02y.

The total invested is $6000: x+ y= 6000

The total interest is $190: .04x+ .02y= 190.

Solve that, then try the others.