I used example numbers. If you need any clarification, let me know.
X=7
Hope this helps and have a wonderful day!
Remember property of exponents

add exponents of same base
ok so
50,000 is 5 times 10^4
so
50000 times 10^15=
5 times 10^4 times 10^15=
5 times

=
5 times 10^19
Answer:
It is given that 5x−3y=k
Now by substituting the value of x and y in the equation
5(3)−3(4)=k
So we get
15−12=k
k=3
Therefore, the value of k is 3
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