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What is the value of x in the equation 3x-y = 30, when y = 15?

What is the value of x in the equation 3x-y = 30, when y = 15?-example-1
User Lyxal
by
3.1k points

2 Answers

5 votes


x=200

Step-by-step explanation:

Okay so we can start by substituting in
y as we know what it is already:


((1)/(5) )x-((2)/(3) )(15)=30

Now at this stage we could use a calculator to figure out what
(2)/(3) of
15 are though a bit of mental math is as easy:


((15)/(3) ) ·
2=
5 ·
2

okay so now we have:


((1)/(5) )x-10=30 add 10 to both sides to get rid of the
-10


((1)/(5))x=40 let's get rid of that fraction by multiplying by
5

and there's the solution for x

We can check we got this right by substituting it back into the original equation with the known y:


((1)/(5) )(200)-((2)/(3))(15)=30

now, and we already know what out of is so :

that means

which is ✓

Therefore we know our solution is right.

User Dhaval Shah
by
3.4k points
1 vote

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User David Jaquay
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3.2k points