The bet function using ProvableAPI 0.5.

ProvableBetFunction.solidity

    function bet(uint stake, uint spinUnder)external notOwner returns (uint spinUnderInput, uint stakeInput, uint prize, uint payout, uint previousBalance){
        require(stake >= minBet && maxBet >= stake , 'stake is outside allowed limits');
        require(spinUnder >= MIN_ROLL_UNDER && spinUnder <= MAX_ROLL_UNDER, 'spinUnder must be between or equal to 11 and 91');
        require(balances[msg.sender] >= stake, 'insufficient balance to cover stake');
        (payout, prize) = getPrizeAndPayout(stake, spinUnder);
        require(balances[owner] >=  (prize.sub(stake)), 'insufficient contract balance to cover the prize');
        previousBalance = balances[msg.sender];
        subtractAmountFromUser(stake);
        uint QUERY_EXECUTION_DELAY = 0;
        uint GAS_FOR_CALLBACK = 200000;
        bytes32 queryId = provable_newRandomDSQuery(
            QUERY_EXECUTION_DELAY,
            NUM_RANDOM_BYTES_REQUESTED,
            GAS_FOR_CALLBACK
        );
        ongoingBets[queryId] = Bet(spinUnder, stake, prize, payout, msg.sender);
        emit logBetStarted(msg.sender, spinUnder, stake, prize, payout, previousBalance);
        return (spinUnder, stake, prize, payout, previousBalance);
    }