Translate into an algebraic expressions: A number increased by a % and decreased by 80% is 400. What is the number ?

(x*(1+a))*0.8 = 400; x = 500/1+a

Step-by-step explanation:

First, increase the number (which we will call x) by a%

x*(1+a) -> You do 1 + a because if you wanted to increase let's say 5 by 20% you would do 5 + 5*0.2 and if you factor that out it becomes 5(1+0.2)

Next, decrease it by 80%.

(x*(1+a))*0.8

Finally, make it into an equation.

(x*(1+a))*0.8 = 400

If you solve it, you get:

x(1+a) = 500

x = 500/1+a