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.

The value of 2 Rs coin could be expressed as 2*5x and the value of 5 Rs coins can be expressed as 5*2x.

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 angles be 7x, 6x, 3x, 2x. Take the sum of total angles to be 360.

Assume the runs scored in 3rd match is x and then create and solve the equation.

Use hit and trial method to complete the equation.

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

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