Remember "PEMA"

Parentheses, Exponents, Multiplication, Addition.   [Remember that division is
a special kind of multiplication, and that subtraction is a special kind of
addition.  Some people use "PEMDAS", but that sometimes makes students think
that multiplication comes before division and that addition comes before
subtraction, when it doesn't.  That is determined by left takes precedence over
right]

Just do one operation at a time, and copy everything else over and don't skip
steps, and you'll always get the right answer.

7[-6+5(-3+5)]

First we look for Parentheses.  The innermost parentheses is (-3+5), so we
replace that by (2) and copy everything else over:

7[-6+5(2)]

We look again for parentheses, the innermost one is now [-6+5(2)], and within 
that parentheses we look for a parentheses.  We find (2) but there is nothing
to do in that parentheses, so we go next to exponents within that set of
parentheses [-6+5(2)].  There are no exponents in there.  So we look for
multiplication and we see 5(2) which we replace by 10 and copy everything else
over:

7[-6+10]

We look again for parentheses, the innermost one is now [-6+10], and within 
that parentheses we look for a parentheses.  Within that there is only -6+10 to
do, so we replace [-6+10] by [4] and copy everything else over:

7[4]

Finally we multiply 7 by 4 and get 28

Answer: 28

Edwin