Multiplying decimals
only do 2-9 i didn't understand it and need . if you it would be great.

On a architect's drawing of a house, 1 inche representa 1.5

Offering 30 if a plus b plus c equals 68 and ab plus bc plus ca equals 1121, where a, b, and c are all prime numbers, find the value of abc. the answer is 1978 but i need an explanation on how to get that.

Roger could feed 5 walruses with 4 kilograms of fish. how many walruses could he feed with 7.2 kilograms of fish?