What is r in the problem d=2r

I'm not sure what you mean by "make the subject."

I can only guess that you'd like to solve this equation for r, which might be what you're looking for.

By "solve this equation for r," what I mean is to rewrite it in the form "r = [some expression]."

This is also known as "isolating."  By performing operations on both sides of the equation the task is achieved.

Step-by-step explanation:

In your example we could begin by dividing both sides by 2, as demonstrated below.

d = 2r

d / 2 = (2r) / 2

d / 2 = r or reversing the equality

r = d / 2.

That didn't require many operations, but the idea is the same for more complicated equations.

Hope this helps.

x > 1.3

step by step:

8.5−0.9x> 9.8−1.9x

step 1: simplify both sides of the inequality.

−0.9x+8.5> −1.9x+9.8

step 2: add 1.9x to both sides.

−0.9x+8.5+1.9x> −1.9x+9.8+1.9x

1x+8.5> 9.8

step 3: subtract 8.5 from both sides.

1x+8.5−8.5> 9.8−8.5

1x> 1.3

step 4: divide both sides by 1.

1x/1 > 1.3/1

graph b

step-by-step explanation:

one solution- graph a (clear intercepting point.)

no solution- graph b (they're parallel, there will never be a point of interception.)

infinite solutions- graph c (all points intercept.)