Even numbers differ by 2. Assume the smallest number is x and then form an equation.

Let the additional kilometres be x and find out the value of x and then add 1 to it for the first km.

Let the breadth be x, form a equation and then solve it. Perimeter is total sum of all the sides

Move all the digit of R.H.S on L.H.S one by one by changing sign and get the value of variable.

Let the age of Lokesh to be x, then form the equation for three years ago.

Assume the number is x, then form an equation and solve the value of x.

Form the equation and then solve it by transpose method.

Let the largest side is x, then form an equation and find the value of x. Perimeter is sum of all the sides.

Take the tens place digit as x and ones place digit as x+4, form the equation and solve for the value of x. Notice that the value of the tens digit would be 10x.

Take the total tree be t and tree which produced the mangoes as (t-8), then solve the equation.