# Video: AQA GCSE Mathematics Foundation Tier Pack 3 β’ Paper 1 β’ Question 14

Work out the value of 3(3π β π) when π = 4 and π = 17.

02:39

### Video Transcript

Work out the value of three times three π minus π when π equals four and π equals 17.

To solve this expression, weβll need to consider our order of operations: brackets, indices, multiplication and division, followed by addition and subtraction. We know that π equals four and π equals 17. So we need to substitute these values in for π and π in the expression. And now our expression looks something like this: three times three times four minus 17. Following our order of operations, we first need to solve what is in the brackets. And inside the brackets, weβll also follow the order of operations.

We donβt have any indices. But we do have multiplication. Three times four equals 12. And then, we bring everything else down. We still need to calculate inside the brackets. But thereβs only subtraction left. 12 minus 17 equals negative five. Bring down the three. And our final step will be multiplying three times negative five which is negative 15. Letβs consider one other way of solving this problem.

Three times three π minus π can be expanded and rewritten. Since weβre multiplying three by everything in the brackets, we could multiply three times three π. We multiply three by the coefficient three and then keep the variable π. Three times three π equals nine π. Now, we need to multiply three by π. Be careful with your sign here. Make sure you bring down that subtraction. π had a coefficient of one. So weβre multiplying three times one which equals three π. Again, make sure you bring down your subtraction. Three times three π minus π is the same thing as nine π minus three π.

And at this point, weβll need to substitute in our values for π and π. And weβll have nine times four minus three times 17. Nine times four is 36. Three times 17 is 51. 36 minus 51 equals negative 15.