How do i solve this and write it in scientific notation?

5.222*10^(-3)




Explanation:

We need to change 5.01*10^(-3) so that the -3 turns into -4. The exponents need to match up so we can add up the bases. To go from -3 to -4, we subtract 1. In other words, we're moving in the negative direction to make the decimal move 1 spot to the left. To counter balance things, we move the decimal of 5.01 one spot to the right to get 50.1

This all means 5.01*10^(-3) is equal to 50.1*10^(-4)

Use a calculator to get
5.01*10^(-3) = 0.00501
50.1*10^(-4) = 0.00501
and we get the same decimal value

So the original expression
( 2.12*10^(-4) ) + ( 5.01*10^(-3) )
turns into
( 2.12*10^(-4) ) + ( 50.1*10^(-4) )



The exponents are now the same so we can add up the bases 2.12 and 50.1 
2.12+50.1 = 52.22

So, 
( 2.12*10^(-4) ) + ( 50.1*10^(-4) ) = 52.22*10^(-4)

Now convert to scientific notation
Move the decimal 1 spot to the left, we need to add 1 to the exponent to counter balance this
52.22*10^(-4) > 5.222*10^(-3)

The final answer is 5.222*10^(-3)

We can check the answer with a calculator
( 2.12*10^(-4) ) + ( 5.01*10^(-3) ) = 0.005222
which converts to 5.222*10^(-3)
This confirms the correct answer.