The sales of a certain product after an initial release can be found by the equation s=16√7t+62 where s represents the total number of units sold and t represents the time in weeks after release. how many weeks will pass before the product sells about 150 units? a. 176 weeks b. 69 weeks c. 4 weeks d. 30 weeks

You want to replace the s with 150 in the equation and then just solve for t.
150=16√7t +62    subtract 62 from both sides
88=16√7t              divide both sides by 16
5.5=√7t                to get rid of the square root  square both sides. 
30.25=7t              now divide both sides by 7
4.3 = t (approximately) 
so at 4 weeks they will have sold 150 units.