Natalie asked the following: could you please show how to work out this question:
stuck on part (b) Thanks for this, Natalie! Let's firstly check you did part (a) right. f(x) is a function  literally a set of instructions of what to do to the value x. So if the function f(x) is to do 74x, then any value of x can be operated on. f(2) means "do the function to x when x=2" So f(2) = 7  4 (2) = 7 + 8 = 15 Now to (b). f(t) means let x=t (t is just another unknown number!) The difference here is that we know what the function did to the number t: it gave the answer 9 So f(t) = 9 means that f(t) = 7  4t (i.e. you just need to set x=t) But we know that f(t) = 9 so 7  4t = 9 is true. So 7 = 9 + 4t
I hope this is clear! Good luck!
