Which letter-cluster will replace the question mark (?) to complete the given series?

REV, UXD, XQL, AJT, ?

Alloy A contains metals x and y only in the ratio 5: 2 and alloy B contains these metals in the ratio 3: 4. Alloy C is prepared by mixing A and B in the ratio 4: 5. The percentage of x in alloy C is:

if $$x-{1\over 5},x≠0,$$ then what is the value of $${x^6+3x^3-1}\over x^6-8x^3-1$$=?

What price should Neeraj mark on a shirt that costs 840, so as to earn a profit of 18% after allowing a discount of 16% on the marked price?

A train travelling at 36 km/h crosses a pole in 25 seconds. How much time (in seconds) will it take to cross a bridge 350 m long?

When positive numbers a, b and c are divided by 13, the remainders are 9, 7 and 10, respectively. What will be the remainder when (a+2b+5c) is divided by 13?

A and B enter into a partnership with capital in the ratio 5: 6. After 4 months, A withdraws $$1\over 5$$of his capital, while B increases his capital by $$33{1\over 3}\%$$. What is the share (in ₹ lakhs) of B in the annual profit of ₹6.3 lakhs?

The value $${7+3\sqrt {5}\over3+\sqrt { 5}}-{7-3\sqrt {5}\over3-\sqrt { 5}}$$ lies between