If the equation 4x+5=45 is equal to the solution of the equation 64-4x=M, then M=how much.
如果方程4x+5=45与方程64-4x=M的解相等，则M=多少．
<gadget id="calculator">45 - 5</gadget>
<output>40</output>

<gadget id="calculator">64 - 40</gadget>
<output>24</output>

<result>24</result>