Which of the following is linear equation.

A seller gives 15% discount on an item, if he marked up the price of item 40% above C.P and while selling he cheats the buyer by giving 10% less in weight. Find this overall profit percent (approximately).

A kite is flying at a height of 123 meter. The thread attached to it assumed to be stretched straight and makes an angle of 60° with the level ground. The length of the string will be 

If two numbers are respectively 20% and 50% of a third number, what is the percentage of the first number to the second?

The sum of two positive numbers is 20% of the sum of their squares and 25% of the difference of their squares. If the numbers are x and y then, is equal to

A circular wire of radius 49 cm is bent in the form of a rectangle whose sides are in the ratio of 6:5 the smaller side of the rectangle is 

A and B can together complete a piece of work in 18 days. B and C can together complete the same work in 24 days and A and C can together complete it in 36 days. In how many days can A. B and C, working together, complete this piece of work?

Three numbers are in the ratio of 3:5:10 and their LCM is 630. Find their HCF.