Given,
The equations are,
[tex]\begin{gathered} x+y=4.25 \\ 16.90x+4y=36.35 \end{gathered}[/tex]
a)The solution of the system represents the number of yards of silk and cotton febric purchased by the dressmakers.
Here, x is the number of yards of silk febric.
y is the number of yards of cotton febric.
b) Taking the first equation as,
[tex]x=4.25-y[/tex]
Substituting the value of x in equation second then,
[tex]\begin{gathered} 16.90(4.25-y)+4y=36.35 \\ 71.825-16.90y+4y=36.35 \\ -12.90y=-35.475 \\ y=2.75\text{ yards} \end{gathered}[/tex]
Substituting the value of y in equation first then,
[tex]\begin{gathered} x=4.25-2.75 \\ x=1.5\text{ yards} \end{gathered}[/tex]
The solution of the system is x = 1.5 and y = 2.75 .
Hence, the number of yards silk and cotton febric purchased by dressmaker is 1.5 yards and 2.75 yards respectively.