Simplify 

(5x+3)+(8x+1) 
(5x)+(8x)= 13x^2 
(5x)+(1)=5x 
(3)+(8x)=11x 
(3)+(1)=4 
=13x^2+5x+11x+4 
=13x^2+16x+4 
Is this right or wrong?

Simplify
(2t^2-3t)-(7t^2-5t) 
= (2t^2)-(7t^2)=-5t 
= (2t^2)-(-5t)= 7t 
=(-3t)-(7t^2)=-10t 
=(-3t)-(-5t)=2t 
=-5t+7t-10t+2t 
I am confused. Why are all my answers "t" and none of them are "t^2"?

3 answers

You do not show any multiplications or divisions in your given problems. All you can do is collect like terms.

(5x+3)+(8x+1)
is the same as
5x+3+8x+1
which is
13 x + 4
===========================
similarly
(2t^2-3t)-(7t^2-5t)

= 2 t^2 - 3 t - 7 t^2 + 5 t

Note that +5 t due to double - sign -( -5 ) = +5

= -5 t^2 + 2 t
Oh okay. So since there is a adding or subtracting sign with brackets, all you do is collect like terms? Okay. So it is not distributive property
no, not distributive property of multiplication

If the question were

(5x+3)(8x+1) no plus sign, so TIMES

then you could say
5x (8x+1)
+
3 (8x+1)

That would be distributive property.