Answer:
y = 21
Explanation:
When x is directly proportional to y:
When x increases, y also increases.
In this case, it is so you write,
1. Write down the formula: y=kx
k being the constant.
Let's use "When x = 4, y = 7" to work out the constant.
2. Substitute the 'when' values: 7=k×4
3. Rearrange to find the constant: 7÷4=k
4. Find k: k=1.75
Now let's see the new problem, 'what is y when x = 12'.
5. Substitute the values now but keep the constant: y = 1.75 × 12
6. Rearrange if needed.
7. Find the missing value: y = 21
Hope this helped and if you require further assistance from me please comment below! :)
Ps: If it was inversely proportional then the formula would be y = k / x
with k still being the constant.