Answer
No solution (inconsistent system)
Work Step by Step
Given: $$\begin{cases}
b &= \frac{3}{10}a +\frac{4}{5}\\
&= 0.3a+0.8\\
b& =0.3a+2.8.
\end{cases}$$ We are asked to use the method of substitution to solve the given system. However, we see that both equations have the same slope but different y-intercepts. This means that the lines are parallel. Since parallel lines do not intercept, the system is inconsistent and has no solution. To further proof this claim, substitute the first equation into the second and solve.
$$\begin{aligned}
0.3a+0.8 &= 0.3a+2.8\\
3a-3a &=2.8-0.8 \\
0 &\not= 2\\
\end{aligned}$$
