7 (1248). The number a is $80 \%$ of the number b, and the number c is $140 \%$ of the number b. Find the numbers a, b, and c, given that c is 72 more than a.
Solution. According to the problem, we have $a=0.8 b, c=1.4 b$,

$$
\begin{gathered}
c-a=72, \text { from which } c-a=1.4 b-0.8 b=0.6 b \\
0.6 b=72, b=120, a=0.8 b=96, c=1.4 b=168
\end{gathered}
$$

Answer: $a=96, b=120, c=168$.

口 8(1249). The number $a$ is $75\%$ of the number $b$ and $40\%$ of the number $c$. The number $c$ is 42 more than $b$. Find the numbers $a$ and $b$.

Solution. According to the problem, we have $a=0.75 b, a=0.4 c$, $c-b=42$. Express $b$ and $c$ in terms of $a: b=\frac{4}{3} a, c=\frac{5}{2} a$, from which $c-b=$ $=\frac{5}{2} a-\frac{4}{3} a=\frac{7}{6} a, \frac{7}{6} a=42, a=36, b=\frac{4}{3} a=48$.

Answer: $a=36, b=48$.