Give me an example for algebraic expressions

Statements reasons 1. ab ? cd; ad ? bc 1. given 2. ac ? ac 2. reflexive property 3. ? adc ? ? cba 3. ? 4. ? dac ? ? bca; ? acd ? ? cab 4. cpctc 5. ? dac and ? bca are alt. int. ? s; ? acd and ? cab are alt. int. ? s 5. definition of alternate interior angles 6. ab ? cd; ad ? bc 6. converse of the alternate interior angles theorem 7. abcd is a parallelogram 7. definition of parallelogram what is the missing reason in step 3?

Hdtv screens usually have a width-to -height ratio of 16: 9. which screen dimensions are in the same proportion?

Which expression is equivalent to the one that is modeled? a) 3x + 4 b) 3(3x + 4) c) 3(x + 4) d) 4(x + 3)