Complementary angles add up to 90 degrees.
So to find A you would need to add A and B together and equal it to 90 (3x+25+5x-7=90)
Combine like terms together (8x+18=90)
Subtract 18 from night sides (8x=72)
Divide by 8 on both sides (x=9)
Then to find A substitute x into its equation (3(9)+25)=(27+25)=52
A=52 I think
