A man travels 30 km in 30 minutes. Calculate his speed in km/h and m/s. Also solve these simultaneous equations: 2a+b=8 and 3a−b=7

Distance ($D$) = $30 \text{ km}$
Time ($T$) = $30 \text{ minutes}$

Since there are $60 \text{ minutes}$ in an hour,

Speed ($S$) is calculated as $S = \frac{D}{T}$.

His speed in kilometers per hour is $\boxed{60 \text{ km/h}}$.

We know that $1 \text{ km} = 1000 \text{ m}$ and $1 \text{ hour} = 3600 \text{ seconds}$.

Rounding to two decimal places, the speed is $\boxed{16.67 \text{ m/s}}$.

29)

Equation (1): $2a + b = 8$
Equation (2): $3a - b = 7$

Add Equation (1) and Equation (2) to eliminate $b$.

Using Equation (1):

The solution is $\boxed{a=3, b=2}$.