помогите плиз 81 номер

х+3.812+13+16=6.5
х+3.836+26+16=6.5
х+3.81=6.5
х+3.8=6.5
х=6.5-3.8
х=2.7

5.7-у57*35*23=8.75
5.7-у 27=8.75
5.7-у=8.75*27
5.7-у=8 34*27
5.7-х=354*27
5.7-у=52
5.7-у=2.5
у=5.7-2.5
у=3.2

х+3.1  415:25+13=7
х+3.1 23+13=7
х+3.1 1=7
х+3.1=7
х=7-3.1
х=3.9