How do you turn a fraction into a decimal?

X/y + 4y/x divided by x/y - 2y/x explain as in depth as you can how you simplfied the fractions. i don't know where to start on this : /

15 liters is approximately how many gallons

Use the second shift theorem to find the inverse laplace transform of (e^−3s) / (s^2 + 2s − 3)