1. The problem shows two expressions with fractions and variables $t$ and $x$ nearby. The expressions are: $$\frac{3+1}{1-1}x$$ $$\frac{3+1}{2-1}x$$ 2. Simplify the numerators and denominators step-by-step: For the first fraction: Numerator: $3+1=4$ Denominator: $1-1=0$ So, the fraction is $\frac{4}{0}$ which is undefined because division by zero is not allowed. For the second fraction: Numerator: $3+1=4$ Denominator: $2-1=1$ So, the fraction is $\frac{4}{1}=4$ 3. Now multiply by $x$: First expression: undefined $\times x$ is still undefined. Second expression: $4 \times x = 4x$ 4. Final answer: - The first expression is undefined because the denominator is zero. - The second expression simplifies to $4x$. Therefore, the only defined and simplified expression is $4x$.