Astudent wrote that there are two terms in the expression 3p - (7 - 4q). explain the student's error.

Expressions are symbols, numbers and operators (such as +, ×, ÷ and -) grouped together that show the value of something.
Example: 4× - 7 is an expression. In 4x-7 =5, 4x, 7, and 5 are called terms.  
Another example is, a student wrote that there are two terms in the expression 3p - (7-4q).
However,  it has three terms, if you are going to evaluate the expression.
Try to observe the expression below. 
3p - (7-4q)
3p- 7 + 4q