 Hello and welcome to the session. In this session we will discuss the following question and the question says, in the formula P is equal to half A plus B square, find A if P is equal to 64, B is equal to 2. Before we start solving the question let us first recall what is subject of a formula, subject of a formula is the variable that is expressed in terms of other variables. So this is our key idea for this question and using this key idea we will solve the question. Let's start the solution now. This problem can be solved in two ways. In the first method we directly substitute the values of the variables and solve. So let's solve the question using method one first. We are given P is equal to half A plus B square. Also it's given in the question that P is equal to 64 and B is equal to 2. Substituting P is equal to 64 and B is equal to 2 we get 64 is equal to half A plus 2 square. This implies 64 is equal to half A plus 4 which implies 64 minus 4 is equal to half A. So we get 60 is equal to half A therefore A is equal to 2 into 60 which is equal to 120. So this is our answer using the first method. Now we will solve this question using method two. In this method we make A as the subject of the formula. Using the key idea we get subject of the formula is the variable that is expressed in terms of other variables. So we express A in terms of P and B. Now we are given that P is equal to half A plus B square. This implies half A is equal to P minus B square. So we have bought terms involving A on one side and terms involving P and B on the other side of equality. This implies A is equal to 2 whole multiplied by P minus B square. So in this way we have made A as the subject of the formula. After this transformation we now substitute the values of P and B. In this formula substituting P is equal to 64, B is equal to 2 we get A is equal to 2 whole multiplied by 64 minus 2 square. This implies A is equal to 2 whole multiplied by 64 minus 4 that is A is equal to 2 into 60. Therefore the answer is A is equal to 120. With this we end our session. Hope you enjoyed the session.