A total of 400 tickets were sold for a concert. The price for a general public ticket was GH¢4.50, and the price for a student ticket was GH¢3.75. A total of GH¢1680 was collected. a) How many tickets

Let $x$ be the number of tickets sold to the general public.
Let $y$ be the number of tickets sold to students.
The price for a general public ticket is GH¢4.50.
The price for a student ticket is GH¢3.75.
The total money collected is GH¢1680.
The total number of tickets sold is 400.

From the total money collected:

$$4.50x + 3.75y = 1680 \quad (1)$$

From the total number of tickets sold:

$$x + y = 400 \quad (2)$$

Multiply equation (1) by 100 to remove decimals:

$$450x + 375y = 168000 \quad (3)$$

From equation (2), express $x$ in terms of $y$:

$$x = 400 - y \quad (4)$$

Substitute equation (4) into equation (3):

$$450(400 - y) + 375y = 168000$$ $$180000 - 450y + 375y = 168000$$ $$180000 - 75y = 168000$$

Subtract 180000 from both sides:

$$-75y = 168000 - 180000$$ $$-75y = -12000$$

Divide by -75:

$$y = \frac{-12000}{-75}$$ $$y = 160$$

Therefore, 160 tickets were sold to students.

The number of tickets sold to students is $\boxed{\text{160 tickets}}$.

Money from general public tickets = Number of tickets $\times$ Price per ticket

$$= 25 \times \text{GH¢}4.50$$ $$= \text{GH¢}112.50$$

Money from student tickets = Number of tickets $\times$ Price per ticket

$$= 20 \times \text{GH¢}3.75$$ $$= \text{GH¢}75.00$$

Mensah.
Total money collected = Money from general public tickets + Money from student tickets

$$= \text{GH¢}112.50 + \text{GH¢}75.00$$ $$= \text{GH¢}187.50$$

Mr. Mensah collected $\boxed{\text{GH¢}187.50}$.