In the e-mail address xab@yahoo.com, “com” stands for ?

If the polynomial ax³ + 4x² + 3x − 4 and x³ – 7x + a leaves the same remainder, when divided by (x − 2), then find the value of a.​

Reduce the equation x⁴ − 13x² + 36 = 0 into a quadratic equation and find the roots of the reduced quadratic equation.

The cost of 3 pens and 12 notebooks is ₹195. The cost of 7 notebooks exceeds the cost of 4 pens by ₹39. What is the cost of 12 pens and 6 notebooks?​

3 bags and 6 pens together cost ₹744, whereas 9 bags and 9 pens together cost ₹1,854. The cost of 6 bags exceeds the cost of 10 pens by:​