How do you do 81x^2=49

Indicate the formula for the following conditions: p^c(n,r)=

Atrain leaves little? rock, arkansas, and travels north at 90 kilometers per hour. another train leaves at the same time and travels south at 80 kilometers per hour. how long will it take before they are 680 kilometers? apart?

Determine the area of a triangle with (see picture below)