1.
5.6 x 10⁴ = 56000
7.8 x 10⁵ = 780000
56000 + 780000 = 836000 or 8.36 x 10⁵
2.
Erica scored 87% while Alex scored 76% on her/his last test. How do we know this? Well, we must convert the fraction into a decmial first.
The fraction is 19/25
We have to do 19 divided by 25 and we'll get 0.76
Then do 0.76 x 100 and you'll get 76
76 = 76%
Therefore the precentage grade is a 11% difference.