With what operators, should the symbols @ and $<$ be replaced so that the following expression is valid.

$100-81÷27$@$3<6=115$

If $Q$ means 'addition sign', $J$ means 'multiplication sign', $T$ means 'subtraction sign' and $K$ means 'division sign' then 

$30K2Q3J6T5=?$

Find the number in place of '?' 

If in a certain code

$23\times 26=42$ and $11\times 15=19$ then, $32\times 16=?$

From each box you can move only to the immediate right box or the immediate top box. You cannot move into or through the shaded box. How many ways are there to move from the  box marked S to the box marked D.

One line forms two regions in a plane. Similarly, two lines in a plane can form maximum of four regions.

These are shown in the figure below.

What is the maximum number of  regions that can be formed by 4 lines in a plane. Lines need not be concurrent.