What is the value of x in the equation 1/5x=-2/3 when y=15

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
=
10
(the dots mean multiply)
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

x
=
200
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
200
5
=
40
and we already know what
2
3
of
15
is so :
that means
40
−
10
=
30
which is ✓
Therefore we know our solution is right.

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