Hey there!!
(1) Both the angles sum up to be 180.
(2) Both the angles sum up to be 90
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(1) 4x+5+8x-5=180
... 12x=180
... x= 180/12
... x = 15
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(2) 4z+3z+6=90
... 7z+6=90
... 7z=84
... z=84/7
... x=12
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Hope it helps!
