$\frac{ \log_{ 10 }({ 3.5 \times {10}^{3}-\left( 1.7 \times {10}^{3} \right) }) }{ 30-40 }$
Remove unnecessary parentheses$\frac{ \log_{ 10 }({ 3.5 \times {10}^{3}-1.7 \times {10}^{3} }) }{ 30-40 }$
Calculate the difference$\frac{ \log_{ 10 }({ 3.5 \times {10}^{3}-1.7 \times {10}^{3} }) }{ -10 }$
Collect like terms$\frac{ \log_{ 10 }({ 1.8 \times {10}^{3} }) }{ -10 }$
Use $\log_{ a }({ x \times y })=\log_{ a }({ x })+\log_{ a }({ y })$ to expand the expression$\frac{ \log_{ 10 }({ 1.8 })+\log_{ 10 }({ {10}^{3} }) }{ -10 }$
Convert the decimal into a fraction$\frac{ \log_{ 10 }({ \frac{ 18 }{ 10 } })+\log_{ 10 }({ {10}^{3} }) }{ -10 }$
Use $\log_{ a }({ {a}^{x} })=x$ to simplify the expression$\frac{ \log_{ 10 }({ \frac{ 18 }{ 10 } })+3 }{ -10 }$
Use $\log_{ a }({ \frac{ x }{ y } })=\log_{ a }({ x })-\log_{ a }({ y })$ to expand the expression$\frac{ \log_{ 10 }({ 18 })-\log_{ 10 }({ 10 })+3 }{ -10 }$
A logarithm with the same base and argument equals $1$$\frac{ \log_{ 10 }({ 18 })-1+3 }{ -10 }$
Calculate the sum$\frac{ \log_{ 10 }({ 18 })+2 }{ -10 }$
Use $\frac{ -a }{ b }=\frac{ a }{ -b }=-\frac{ a }{ b }$ to rewrite the fraction$\begin{align*}&-\frac{ \log_{ 10 }({ 18 })+2 }{ 10 } \\&\approx-0.325527\end{align*}$