For the first question you need to find the greatest common factor. Start by trying 2 and work your way up. 2 does not work because it will not go into 35 or 63. 3 does not go evenly into 35. 4 also will not work. 5 does not work. 6 also will not work. . .Then we come to 7. . .if we divide each number by 7 we get the following:
6:5:9
We know this is in lowest simplist form because 5 is a prime number.
Next we need to convert kilograms to grams by multiplying by 1000 to get
35000 g : 1400 g
in this case the greatest common factor is 1400 which if we divide both numbers we get
25 g : 1 g
For the final question we should convert to mm
2.5m=2500mm
75cm=750mm
350 mm : 2500 mm : 750 mm
We know that 50 will go evenly into each of these and we know that 350/50 is 7 which is prime. So 50 must be the greatest common factor. Divide all 3 terms by 50 and we get
7 mm : 50 mm : 15 mm