A car travels from A to B at 20 km/h and returns along the same road at 30 km/h. Find the average speed for the whole journey.

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Simplify $\frac{( 3 x ^{2} y ^{- 3} ) ^{2}}{9 x y ^{2}}$ and express your answer with positive indices.
The marked price of a watch is increased by $20%$ and then sold at a discount of $25%$ . What is the overall percentage change in the price…
Solve the simultaneous equations ${2 x + 3 y = 7 3 x - 2 y = 4$ . What is the value of $x + y$ ?
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