5×7-20=____ 62-72÷9=____ 70+3×6=____
15+42÷6=____ 8×6+30=____ 42÷7÷2=____
5×(32-24)=____ (16+8)÷3=____ 28-(26-20)=____
计算:
(1)若xm•x2m=2,求x9m的值;
(2)已知3×92m×27m=315,求m的值.