Răspuns:
a) x+45=87
x=87-45
x=42
f) 345+123=x+235
468=x+235
x=468-235
x=233
b) x+1235=7325
x=7325-1235
x=6090
g) 3104-(415-x)=300
-415+x=3104-300
-415+x=2804
x=2804+415
x=3219
c) 13702 - x=12721
x=13702-12721
x=981
h) 42 + (x - 24) = 2302
x-24=2302-42
x-24=2260
x=2260-24
x=2236
d) x - 3514 = 7235
x=7235+3514
x=10749
i) 2345 - 1234 + x = 7213 - 2513
Explicație pas cu pas:
a) 118+90-121=x (cand treci un numar dintr-o parte in alta i se schimba semnul)
208-121=87
b) x=-15+2+25
x=-13+25=12
c) *aici aplici metoda mersului invers*
400-(50+x)=100
400-100=50+x
300-50=x
x=250
d) 80+70-40+x=435
110+x=435
x=435-110=325 (: