We will find the distance from point A to the line as follows:
*First: We solve for 0 on the equation of the line, that is:

Now, we can see that the equation of the line has the form:

So, we use the following expression to determine the distance from the point to the line:
![d=\fracAx_1+By_1+C{\sqrt[]{A^2+B^2}}](https://img.qammunity.org/2023/formulas/mathematics/college/9zp3ooor99yjg6ys87qljriamw05517393.png)
Now, we replace the values and solve for d:
![d=\frac(5)(15)+(4)(-21)+(-4){\sqrt[]{5^2+2^2}}\Rightarrow d=\frac-13{\sqrt[]{29}}](https://img.qammunity.org/2023/formulas/mathematics/college/59krmr063epjhatokdghns53puhfpkzj72.png)
![\Rightarrow d=\frac{13}{\sqrt[]{29}}\Rightarrow d\approx2.4](https://img.qammunity.org/2023/formulas/mathematics/college/ua3t8kv4uuqz8f65lrg9f7r07zqlay2fee.png)
So, the distance from point (15, -21) to the line 5x + 2y = 4 is approximately 2.4 units.