Break down this math problem: Julia and Nadine were given the same amount of allowance by their mother. The two girls decided to combine their allowance to surprise their father on his birthday. They bought a cake which costs $11. They also bought 1 dozen balloons which were sold for $0.5 for 2 balloons. The remaining money was used to buy 2 tubs of ice cream for $7 each. How much did Julia and Nadine's mother give each one of them?