I1.1 Given that $\frac{3}{a}+\frac{1}{u}=\frac{7}{2}$ and $\frac{2}{a}-\frac{3}{u}=6$ are simultaneous equations in $a$ and $u$. Solve for $a$.
I1.2 Three solutions of the equation $p x+q y+b z=1$ are $(0,3 a, 1),(9 a,-1,2)$ and $(0,3 a, 0)$. Find the value of the coefficient $b$.

I1.3 Find $c$ so that the graph of $y=m x+c$ passes through the two points $(b+4,5)$ and $(-2,2)$.
I1.4 The solution of the inequality $x^{2}+5 x-2 c \leq 0$ is $d \leq x \leq 1$. Find $d$.
$$
\begin{array}{c}
3(1)+(2): \frac{11}{a}=\frac{33}{2} \\
a=\frac{2}{3} \\
\left\{\begin{array}{c}
3 a q+b=1 \\
9 a p-q+2 b=1 \\
3 a q=1
\end{array}\right.
\end{array}
$$

Sub. (3) into (1): $1+b=1$
$$
\Rightarrow b=0
$$

The 2 points are: $(4,5)$ and $(-2,2)$. The slope is $\frac{5-2}{4-(-2)}=\frac{1}{2}$. The line $y=\frac{1}{2} x+c$ passes through $(-2,2): 2=-1+c$
$$
\begin{array}{l}
\Rightarrow c=3 \\
x^{2}+5 x-6 \leq 0 \\
\Rightarrow(x+6)(x-1) \leq 0 \\
-6 \leq x \leq 1 \\
d=-6
\end{array}
$$