1)
(15+17)*14/(42*8)=4/3=1 1/3
2)
(53*4/53+5/4)*5/21=21/4*5/21=5/4=1,25
3)
((9*3+34*2)/12)*5/17-5/4=475/204-5/4=(475-255)/204=55/51=1 4/51
4)
((13*3+23*2)/12)/((23*3-11*4)/12)=85/25=17/5=3,4
5)
((34*4-11*5)/20)/((58+11*7)/21)=81/20 * 21/135=1 701/2 700=0,63