difficult

"The teacher is requiring students to submit their essays by Friday. "

"My teacher explained the new math concept, and I understood it perfectly. "

"Instruction will be provided on how to handle difficult customers."

"The computer has been very troublesome for me. It never works when I need to use it."

"The program will run smoothly under these conditions: the computer has enough memory and the internet connection is stable. "

"The new school management software allows teachers to easily track student progress. "

"We are unwilling to restore his previous privileges after his betrayal of our trust."

"Understanding mathematical concepts is crucial for solving complex problems. "

"He completed the assignment on time."

"The child was uncooperative during bath time, refusing to sit still or let his hair be washed. "

"The fish in the aquarium needed freshwater, not saltwater. "

"The teacher complicated the math problem by adding several extra steps. "