Answer:
"He loved her style so much that he wanted her to sell her pieces...And even though he understood, he’d become increasingly frustrated; he desperately wanted to show her work to the greater public."
Step-by-step explanation:
Marcus greatly believes in Ariana's talents as an artist, and the evidence from the text that supports this conclusion is the fact that he loved her work so much and was desperate to put it in a gallery so that the public would come and view it.
Marcus loved Ariana's style in painting and was eager to help her show her work to the world.