(1)设这个数为x,由题意得:
2x+3.8=4.6,
2x=0.8,
x=0.4;
答:这个数是0.4.
(2)18÷(1.5+0.75)+2.4,
=18÷2.25+2.4,
=8+2.4,
=10.4.
答:和是10.4.