Given:

• Letters P, Q, R, S, T represent numbers 4, 5, 10, 12, 15, respectively.
• Q−S=2S or Q = 3S … (Equation 1)
• T=R+S+3 … (Equation 2)

Analysing Equation 1: Q = 3S

• To satisfy this, from the given numbers, the values of S can be either 4 or 5.
• Hence, Q can be either 12 or 15.

Analysing Equation 2: T=R+S+3

• Case 1: if S = 4 and Q = 12: T, R, S will be chosen from 5, 10, 15. No combination will fit in T=R+S+3. Hence, this case is not possible.
• Case 2: if S = 5 and Q = 15: T, R, S will be chosen from 4, 10, 12. If we take R = 4, and T = 12, then 12 = 4 + 5 + 3, which is true.

Finding the value of P + R – T

• We have, S = 5, Q = 15, R = 4, and T = 12, P = 10
• Hence, P + R – T = 10 + 4 – 12 = 2.

Hence, option b is the correct answer.