Where to spend my money: Stocks vs. Mortgage vs. Student Loan?

Hello Everyone, I owe about $150,000 in my mortgage (3.75%), $150,000 in my student loans (private with variable rate of 2.85% currently), and I make about $150,000 in income. I'm trying to decide whether to pay off the mortgage first given the higher rate, invest in the stock market with vanguard or wealthfront, or take out the variable rate loan first. I know the market traditionally goes up 7% so on the outset that seems like the best option, but the tax consequences of doing so gives me concern and has me leaning towards the home mortgage. Advice would be appreciated! Thanks.