Environmental issues are a serious concern for the people of sub-saharan africa because

Environmental issues are a serious problem for the people of Sub-Saharan Africa because they depend upon the land for their livelihoods... 

b) their livelihoods are derived from the land.

Explanation:

Deforestation, desertification, soil erosion, and wetland degradation are some of the serious causes and consequences of the problems that today's sub-Saharan Africa faces. Thus these environmental problems account for the 80% share of the problems that the developing country faces and the vast majority of people still dependent o the agricultural lands. Some other factors like the foreign debts on the lands and the increasing population that adds to the pressure on the lands. People, on the whole, can play a crucial role to derive the change.

343^x = 49^4-xx = 4-xx+x=42x = 4x = 4/2x = 2therefore x = 2