50-55 +4+=15
30 + 55-6t=7
-r+ 55-5t=20

I wanted to point out that you can't solve this equation because the question you gave us isn't properly formatted and isn't true at the moment... Unless they are 3 different problems. Which I have solved below.

Let's start off with the first question.

50 - 55 + 4 = 15

You would first simplify each side to find...

-1 = 15

Which isn't true meaning this question is unsolvable.

Now, moving onto the second question.

30 + 55 - 6t = 7

You again would start off by simplifying each side.

85 - 6t = 7

Then you should add 6t to each side to get rid of the negative 6t.

85 = 7 + 6t

After that, you should subtract 7 from each side so that you have isolated the variable.

78 = 6t

And the you would divide each side by 6 to get the answer for t.

t = 13

Now, the final question. I will be solving for both r and t in this question. Let's start with solving for t first.

-r + 55 - 5t = 20

You would start off by add 5t to each side to begin the isolation of t.

-r + 55 = 20 + 5t

Then you would subtract 20 from each side to completely isolate the variable.

-r + 35 = 5t

Now you would divide 5 from both sides to just get t.

-r/5 + 7 = t

And that's your answer for t.

To get r, you would begin again by trying to isolate the r. You would add r to both sides to try and isolate r.

-r + 55 - 5t = 20

And you would get...

55 - 5t = 20 + r

Now you would subtract 20 from each side to get r alone...

35 - 5t = r

And that's your answer for r.

the answer is 5/3x+7/5y+7

its 8

step-by-step explanation: