Answer:
The bottom left one
15 - (50 / 10) 
Explanation:
15 minus the quotient of 50 and 10 
Keywords:
Minus: subtraction meaning we would use (-) 
Quotient: Quotient is the outcome of division (/) 
15 minus the quotient of 50 and 10 
Replace minus with (-)
15 - the quotient of 50 and 10 
Get rid of quotient and add a division sign between 50 and 10 
15 - 50 / 10 
Add parenthesis
15 - (50 / 10 )