Respuesta :

 you cant add or subtract or multiply or divide if the variables arent the same so the simplified version of -3x²ym + 7x - 5ymx² + 16x would be 
 -3x²ym - 5ymx² + 23x
I got -8mx^2y + 23x , you may review the image i've attached to see how I got my answer.
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