which value of x makes this equation true

Answer:
65
Step-by-step explanation:
Let's find
[tex] \sf \hookrightarrow \: 35 + 42 = 12 + x \\ \sf \hookrightarrow \: 77 = 12 + x \\ \sf \hookrightarrow \: x = 77 - 12 \\ \sf \hookrightarrow \: x = 65[/tex]