Pre-heat your oven to 350F.
First mix your strawberries, rhubarb, 1/2 cup of sugar, 1/2 cup of brown sugar, and corn starch together.
Roll out your pie crust into a pie dish. Place your filling into the pie dish. Place your pie into the oven, without the top. Now mix your butter, the rest of your sugar, baking soda, and flour together. You are making almost like a biscuit topping.
As you mix it all together it should start to form a crumbly mixture. Form the mixture into balls and roll them out over the filling (after you have seen the filling turn a bright red). That should take about 20 minutes.
Lay the biscuit topping over the filling. Bake in the oven, the topping should turn a golden brown.