.
1.  The phone percent charging 
        =  expressed as the decimal fraction,   or
        =
     expressed as the decimal fraction,   or
        =   expressed as percentage,
    where t is time in minutes.
2.  The tablet percent charging 
        =
        expressed as percentage,
    where t is time in minutes.
2.  The tablet percent charging 
        =  expressed as the decimal fraction,   or
        =
      expressed as the decimal fraction,   or
        =   expressed as percentage,
        =
       expressed as percentage,
        =   ,       expressed as percentage,
    where t is time in minutes.
,       expressed as percentage,
    where t is time in minutes.
Solved.