What is the value of a?

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?