Form the pair of linear equations in the following problems, and find their solutions graphically. 

(i) 10 students of Class X took part in a Mathematics quiz. If the number of girls is 4 more than the number of boys, find the number of boys and girls who took part in the quiz. 

(ii) 5 pencils and 7 pens together cost ₹50, whereas 7 pencils and 5 pens together cost ₹46. Find the cost of one pencil and that of one pen.

(i) Let the number of girls be x and the number of boys be y.

According to the question, the algebraic expression can be represented as follows: x + y = 10 and x – y = 4

For, x + y = 10, the solution table is:

For, x - y = 4, the solution table is:

The graphical representation is shown below:

From the graph, it can be seen that the given lines cross each other at point (7, 3). Therefore, there are 7 girls and 3 boys in the class.