Mathematical operations on variables in JavaScript

Mathematical operations can be performed not only on numbers, but on variables too. Let's add, for example, values of two variables:

let a = 1;
let b = 2;
alert(a + b); // shows 3

It is not necessary to display the result of the operation immediately, you can first write it to some variable, and only then display the value of this variable:

let a = 1;
let b = 2;
let c = a + b; // write the sum to the variable c
alert(c);      // shows 3

Create the variable a with the value 10 and variable b with the value 2. Display their sum, difference, product, and quotient (division result).

Create the variable c with the value 10 and variable d with the value 5. Sum them up and assign the result to the variable result. Display the value of the variable result.

Create the variable a with the value 1, variable b with the value 2 and variable c with the value 3. Display their sum.

Create the variable a with the value 10 and variable b with the value 5. Subtract from a the variable b and assign the result to variable c. After, create the variable d, assign the value 7 to it. Add the variables c and d, then write the result to the variable result. Display the value of the variable result.