what's wrong with my code below?

Question

fun main(args: Array<String>) {

var a=readLine()!!.toDouble();
var b=readLine()!!.toDouble();
val Double c="subtraction is${a-b}"
print(c);
}

Answer 1

in Sololearn you can only ask input for one time.
Also you are storing a string into a double variable.

If you want to declare a type of a variable
val b : Double = 3.5;

fun main(args: Array<String>) {

var a : Double = readLine()!!.toDouble();
var b : Double = readLine()!!.toDouble();
val c = "subtraction is " + (a-b);
print(c);

}