Math Zero To Hero

Let's try to solve this math :
The cost price of 40 pens is the same as the selling price of x number of pens. If the loss is 20% ,what is the value of x ?

Let's try to solve this math :
X sells an item to Y at a profit of 28% on his cost and Y sells the same item to Z at a loss of 25% on his cost . If Y thus sold the item to Z at Tk.2 less than the cost of the item to X, What is the cost of the item to X in Taka?

Let's try to solve this math :
The percentage profit earned by selling an article for Tk. 1920 is equal to percentage loss incurs selling the same article for Tk. 1280 . At what price should the article be sold to make 25% profit ?

Lets try to solve this problem :

The average of four consecutive even numbers is 27 .The largest of these numbers is ?

Lets try a problem

A fruit seller buys lemons at 2 for a Taka & sells them at 5 for 3 Taka .His gain percent is?
A) 10% B) 15% C) 20% D) 30% E) none

Lets try a problem

The amount of tax paid by an executive remains constant despite an increase of tk. 2000 in his salary because the rate of the tax was reduced from 15% to 12%. if 30% of his income was exempted from tax in both the cases what was his salary (in taka) before rise?
A) 8000
B) 10000
C) 12000
D) 13500
E) none of these