The system of equations x + y + z = 6, 2x + y + z = 7, x + 2 y + z = 8 has a. A unique solution b. No solution c. An infinite number of solutions d. None of these

Person X can solve 80% of the ISRO question paper and Person Y can solve 60%. The probability that at least one of them will solve a problem from the question paper, selected at random is : a. 0.48 b. 0.70 c. 0.88 d. 0.92

There is a function f(x), such that f(0) = 1 and f ' (0)= -1 and f(x) is positive for all values of x. Then, a) f"(x) < 0 for all x b) -1 < f'' (x) < 0 for all x c) -2 < f '' (x) < -1 for all x d) None of the above