What value should come in place of the question mark (?) in the following question?

52x14+145018=1998÷?

What is the simplified value of (cos A + sin A)(cot A + tan A)?

If x + [1/(x + 7)] = 0, then what is the value of x – [1/(x + 7)]?

If two successive discounts of 50% and 10% are offered, then what is the net discount (in %)?

If sec2θ + tan2θ = 5/3, then what is the value of tan2θ?

A square is inscribed in a quarter circle in such a way that two of its adjacent vertices on the radius are equidistant from the centre and other two vertices lie on the circumference. If the side of square is √(5/2) cm, then what is the radius (in cm) of the circle?

How many diagonals are there in octagon?

ABCD is a parallelogram in which AB = 7 cm, BC = 9 cm and AC = 8 cm. What is the length (in cm) of other diagonal?

In the fig. ∆ABC is inscribed in a circle with centre O. If ∠ABC = 30° then ∠ACB is equal to