Can you explain the equation of X, how do we get 4, is it a hypothetical number?

I want a correct explanation
 

For the game with the following payoff matrix, determine the optimum strategies and the value of the game: B A 4 A, B B S = and S= Pz 9: [P P+P=1,q,+q=1 If E(p,q) denotes the expected payoff function, then E(p.q)= 5p1q: +3(1-p1)q: +1p1(1-4)+4(1 - p)(1-91) =5p141-3p1-91 +4 =5(pi-1/5)(q1-3/5)+17/5 If p = 1/5, A ensures that his expectation is atleast 17/5. A can't be sure of more than 17/5, because q = 3/5, B can keep E(p141) down to 17/5. Hence optimum strategy for A and B are: Az -575]-SA-3/5 2/5] and the value of the game is v = 17/5 4=3+x 4- = x X = X= 3525 20 17 5 35