Start with

Subtract
from both sides:

Divide both sides by 

And thus we solved the expression for l:

Answer:
for question #1) 6 times n + 12 = 60
Step-by-step explanation:
it works trust me
ps. im in high school in a GT math class
5x10^5
0.000023 + 0.0000078= 0.0000308
3.8x10^-6
i think
sorry if wrong but i dont know the second one that well