Rechel needs a mixture of nuts containing peanuts and cashews of 46 pounds.
This means that the sum of peanuts and cashews must be equal to 46 pounds.
Let p denotes the number of pounds of peanuts.
Let c denotes the number of pounds of cashews.
Then we can write the following equation
Let us make c the subject of the equation
Therefore, the expression for the number of pounds of cashews that Rachel needs to add is 46 - p