Acomputer that originally cost $850 is on sale for 15% off. what is sale price of the computer?< 3 !

Percent means per 100
think cent as in 100 pennies in a dollar

To convert from percent to decimal, we divide by 100 or move the decimal over 2 spots, so,
15% = 15/100 = 0.15

Now multiply 0.15 by 850 to find the discount saved
0.15*850 = 127.50
So you'll save $127.50

The final price is therefore: 850-127.50 = 722.50

A shortcut is to multiply 850 by 0.85 
850*0.85 = 722.50
We get the same answer
The 0.85 comes from the fact that if you get 15% off, then you pay 85% of the original price

$722.50