2. 14x+15x, or 29x (simplified form)
3. 27x+5x, or 32x (simplified form)
4. 64x+6x, or 70x (simplified form)
Hope this helps.
I dont really know if this is right myself, but i'm just using the skills my teacher thought me.
3 cm because 6÷2=3 from your helpers
So say you are adding 1/2 and 1 1/2
you would turn the mixed number into a improper fraction by multiplying the denominator by the whole number, then add it to the numerator
for this example it would be 2 x 1 = 2 + 1 = 3 then put it over the denominator
we would get 3/2 then we add 1/2 to it getting 4/2,
then depending on the question we would either leave it as an improper fraction like 4/2 or we would turn it to a mixed fraction, 2 but it will not always be a whole number like this.
like for example if this problem was 1/4 + 1 2/4 we could get 1 3/4
I hope that this helped you somehow because I tried to explain this to the best of my ability.
You would need 105 of sodium I found how much increase there was from 30 to 75 by doing 75/30 which is 2.5 that means the new amount of sodium would be 2.5 times 42 which is 105. You could also set up ratios and cross multiply like the picture I sent