Complete the proof. (look at the image attached)

Aresearch company wants to test the claim that a new multivitamin to improve short term memory. state the objective of the experiment, suggest a population, determine the experimental and control groups, and describe a sample procedure.

You give a $4 tip for a meal that cost $22. approximately what percent of the bill was your tip?

Can some one explain how to slove specifically, what is the value of x? 0.9(x+1.4)-2.3+0.1x=1.6 enter the answer as a decimal in the box. x= ?