Answer
$-\dfrac{16}{45}$
Work Step by Step
Find the LCM of the denominators:
$30 = 5(2)(3)
\\18=2(3)(3)$
The LCM is $5(2)(3)(3) =90$
Thus, the LCD is also $90$
Make the fractions similar using their LCD to obtain:
$=\dfrac{1(3)}{30(3)} - \dfrac{7(5)}{18(5)}
\\=\dfrac{3}{90}-\dfrac{35}{90}
\\=\dfrac{3-35}{90}
\\=\dfrac{-32}{90}$
Simplify by canceling the common factor $2$ to obtain:
$\require{cancel}
=-\dfrac{\cancel{32}^{16}}{\cancel{90}^{45}}
\\=-\dfrac{16}{45}$
