Khalid invested $9500 in a savings account with a yearly interest rate of 3% for 8 years. How much simple interest did he earn?

So simple interest, you don't compound anything, you will always add 3% from $9500 and it will not change. The equation will look like this:

9500*[1 + (0.03*8) ]

giving us 9500*1.24 = $11,780