An arc subtends an angle of 72\(^o\) at the centre of a circle. Find the length of the arc if the radius of the circle is 3.5 cm. [Take \(\pi = \frac{22}{7}\)]

Make b the subject of the relation lb = \(\frac{1}{2}\) (a + b)h

Eric sold his house through an agent who charged 8% commission on the selling price. If Eric received $117,760.00 after the sale, what was the selling price of the house? 

Find the angle at which an arc of length 22 cm subtends at the centre of a circle of radius 15cm.  [Take \(\pi = \frac{22}{7}\)]

A rectangular board has a length of 15cm and width x cm. If its sides are doubled, find its new area.