Step 1: Write down the known variables

$$

\begin{aligned}

A &=45000 \\

P &=30000 \\

i &=0,075

\end{aligned}

$$

Step 2: Write down the formula

$$

A=P(1+i n)

$$

Step 3: Substitute the values and solve for $n$

$$

\begin{aligned}

45000 &=30000(1+0,075 \times n) \\

\frac{45000}{30000} &=1+0,075 \times n \\

\frac{45000}{30000}-1 &=0,075 \times n \\

\frac{\left(\frac{45000}{30000}\right)-1}{0,075} &=n \\

n &=6 \frac{2}{3}

\end{aligned}

$$

Step 4: Write the final answer

It will take 6 years and 8 months to make $\mathrm{R} 45000$ from $\mathrm{R} 30000$ at a simple interest rate of $7,5 \%$ p.a.