1.004 * 10^5
all scientific notation equations have to be a number greater than 1 but less than 10
then multiplied by 10 to the power of (move the decimal point to the right however many times you need, in this case 5) :)
The answer is 12.
Steps
If that number is x
(3+x)/(8+x)=3/4
"Cross multply"
4(3+x)=3(8+x)
12+4x=24+3x
x=12
To check: add 12 to 3 and 8. 3+12=15 and 8+12=20. 15/20=3/4