To change fractions to decimal: Divide the numerator by the denominator.
Ex. 4/5 = 4÷5 = 0.80
Decimal to fractions: Count first the number of decimal places and write it as a whole number over 10^x where x is the number of decimal places and give the fraction into lowest terms.
Ex. 0.625 (has 3 decimal places)
625/10³ = 625/1000 (convert to lowest term) = 5/8
Standard form to Scientific notation: First, move the decimal point the required amount, to make the number's value within a desired range, between 1 and 10. Then multiply it by 10^x. To get the value of x, count the number of place values you passed as you moved the decimal point.
Ex. 178,000,000 ⇒ 1.78x10⁸