Scale 5-15V to 30-50V using op amp
You are looking to step up the input voltage ranging from 5-15 to 30-50Volts. This calls non inverting amplifier where the you need to choose Rf and Rin resisters such that the ratio of  (Rin+Rf)/Rin  is 6. This will help acheive 30 V when the input is 5 V.