The difference (-) between 3 times a number (3n) and 21.
3n - 21
You would need to see the rest of the equation to plug in 7 for x. Treat it as y=equation and replace any x with 7.
Answer:
35
Step-by-step explanation:
x + 55 = 90
x = 90 - 55
x = 35
Let's start by understanding that the graph is a linear line. We have a common difference if 4.5 for every 10x we have more.
We can start by finding the gradient, using rise over run. Let's take (10, 4.5) and (20, 9)
Our rise is 9 - 4.5 = 4.5 and our run is 10. Then, our gradient becomes 4.5/10 = 0.45
Now, we can substitute points using the point-slope form.
y - 4.5 = 0.45(x - 10)
y - 4.5 = 0.45x - 4.5
Hence, our line becomes y = 0.45x and you can verify by substituting in points from the table.
