If I didn't take 4 years of math in high school and have graduated, is there a way I can get a 4th math credit to get into the college I want?

Hi guys, I'm freshly graduated and chose to take a gap year to save money for college and to figure out what I want to do - it took a lot less than a year to figure out what I want to. I want to go to the Milwaukee School Of Engineering for BioMolecular Engineering and I meet (or surpass) all of the requirements - except one. I didn't take 4 years of math (I originally hadn't taken a 4th math credit for my senior year. After school started I tried to switch classes to get a math credit, but my school wouldn't let me.)

Is there a way, maybe through some online program, that I can get a 4th math credit to be able to get into MSOE?