Read this directions

a poor girl out with geometry lol the directions are: find the missing side. round to the nearest tenth. i know it has to do with tangents and stuff.
the directions for 136 is determine if line ab is tangent to the circle.
the directions for 138 is find the segment length indicated. assume that lines which appear to be tangent are tangent. the directions for 140 is solve for x. assume that lines which appear to be tangent are tangent

What is the approximate circumference of the circle shown below? 12.2 cm

Suggest two reasons why irrigation is important for human development of the desert (4 marks)

70 pts answer the following questions in full sentences and paragraphs, using at least 150 words, in the essay box below. 1. which organisms are carnivores? herbivores? omnivores? 2. if the ecosystem is balanced, which populations should be the largest? the smallest? 3. imagine a group of hunters kills half of the rabbit population. how will the other organisms be affected? 4. imagine disease kills 85 percent of the wolf population. how will the other organisms be affected? 5. imagine a foreign mountain lion species is introduced into the ecosystem. how will the other organisms be affected?