In 2-quart saucepan, mix sugar, tapioca, cornstarch and salt. Stir in reserved cherry juice and strawberry syrup. Heat over medium heat, stirring constantly, 5 to 10 minutes or until juice becomes thick and boils. Remove from heat. Stir in cherries, strawberries and lemon juice. Pour into crust-lined pie plate. Dot with butter. Place second crust over filling. Flute, and cut slits in top crust to vent.