# Question Video: Solving Two-Step Linear Equations in Real-World Contexts

The difference between an ostrich’s speed and a chicken’s speed is 31 miles per hour. If an ostrich can run at a speed of 40 miles per hour, solve the equation 40 − 𝑐 = 31 to find the speed a chicken can run 𝑐.

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### Video Transcript

The difference between an ostrich’s speed and a chicken’s speed is 31 miles per hour. If an ostrich can run at a speed of 40 miles per hour, solve the equation 40 minus 𝑐 equals 31 to find the speed a chicken can run, 𝑐.

We need to solve the equation 40 minus 𝑐 equals 31 to calculate the value of 𝑐. The 31 represents the difference in speeds between the ostrich and the chicken. The 40 represents the speed of the ostrich. The unknown 𝑐 that we are trying to calculate is the speed of the chicken.

Our first step to solve the equation is to subtract 40 from both sides. 40 minus 40 is equal to zero, so the left-hand side becomes negative 𝑐. 31 minus 40 is equal to negative nine. This gives us negative 𝑐 is equal to negative nine.

Our final step is to multiply both sides of the equation by negative one. Multiplying two negative numbers gives us a positive answer. So, we are left with 𝑐 is equal to nine. If the difference between the ostrich’s speed and chicken’s speed is 31 miles per hour, and the ostrich can run at a speed of 40 miles per hour, then the speed of the chicken is nine miles per hour.