El método mas adecuado para resolver un sistema de ecuaciones con dos incógnitas

Ascientist wants to find the radius in meters of his hemispherical dome he found that the surface area of the entire sphere containing the dome is 682 square meters which equation could he use to find the domes radius

When graphing a linear equation that is written in the form y=mx+b, the variable m represents the y-intercept. assuming that b> 0, which of the following best describes how reversing the sign of b would affect the graph? a) the new line will be shifted down b units b) the new line will be shifted down b x 2 units c) the new line will be a perfect reflection across the x-axis d) the new line will be a perfect reflection across the y-axis

How do you work out 21.3-8= show your working. plz