Yes. It is possible to construct a triangle with the given measurements.
Step 1: draw the constant base I.e QR=7cm.
Step 2: construct ∠R =45° on point R.
Step 3: extend ∠R to mark point P. I.e RP = 5cm.
Step 4: join PQ. Measure PQ which will be = 5cm
The construction will be like this