It makes the addition easier if you combine like terms like the two 1/2s and then make them all have the denominator of 12 (changing the numerators to equal it out)
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
It reflects across the x axis